Positive displacement machines working as hydraulic pumps or hydraulic motors have always been, are and will be an essential part of any hydraulic system. Current trends and future demands on energy efficient systems will not only drastically increase the number of positive displacement machines needed for modern efficient hydraulic circuits but will significantly change the performance requirements of pumps and motors. Throttleless system configurations will change the landscape of hydraulic actuation in aerospace, mobile machines, automotive and many other areas and will definitely open the door for new applications due to its enhanced competitiveness with electric and electro-mechanical systems.

Until recently, hydrostatic-mechanical power split CVT drivelines have not found a place in construction machinery. The majority of these vehicles still use hydrodynamic powershift transmissions, full-hydrostatic transmissions or mechanical direct-shift transmissions. Hydrostatic drive lines are widely used in construction machinery possessing lower engine power. The upper power range is dominated by hydrodynamic powershift transmissions. Decisions made by vehicle manufacturers about which driveline technology to be used, have been based mainly on reliability, durability, and cost. Fuel economy has also been a growing trend over the past years; however the additional cost of higher technologies must be compensated by the savings in fuel cost over a time period of 2-3 years. The transmission’s efficiency highly contributes to the vehicle’s fuel consumption. ZF has thoroughly studied the possible concepts of hydrostatic-mechanical power split transmissions. The most important requirements of reliability, durability and efficiency were taken into consideration during the concept study. An examination the most typical working cycles showed that a construction machinery transmission needs to be fully power split in all ranges and obtain equal performance in both driving directions. It was also observed that up to 60% of productive time for construction and forestry equipment was spent at a speed below 12 km/h. For this speed range, achieving the highest possible efficiency is vital. The result of this research is the ZF cPower, which is an output-coupled, fully power split transmission.

The International Fluid Power Conference is one of the world's most significant scientific conferences on fluid power control technology and systems. It offers a common platform for the presentation and discussion of trends and innovations to manufacturers, users and scientists.

Group A: Digital Hydraulics Group B: Intelligent Control Group C: Valves Group D | G | K: Fundamentals Group E | H | L: Mobile Hydraulics Group F | I: Pumps Group M: Hydraulic Components

10. Internationales Fluidtechnisches Kolloquium

10. Internationales Fluidtechnisches Kolloquium

Independent metering poses a possibility to improve energy efficiency of throttlecontrolled hydraulic single-rod cylinder drives. This paper deals with energetic potentials gained through variable circuitry that come along with independent metering. A method to assess energetic potentials is described, based on load specific, optimal operating modes. As a means of yielding maximum energy efficiency for a wide range of applications, a smooth mode switching algorithm that minimizes losses and allows good motion tracking is proposed. The mode switching algorithm is validated in simulation and on a test stand.

Bulk modulus of hydraulic oil represents the resistance of hydraulic oil to compression and is the reciprocal of compressibility. The bulk modulus is a basic thermodynamic property of hydraulic oil that has a very important influence on work efficiency and dynamic characteristics of hydraulic systems, especially for the hydraulic systems at ultra-high pressure or ultra-high temperature. In this study, a bulk modulus experimental equipment for hydraulic oil was designed and manufactured, two types of hydraulic oil were selected and its isothermal secant bulk modulus were measured at pressures to 140MPa and temperatures of 20~180°C. Compared the experimental results with the calculated results from the prediction equations of liquid bulk modulus that proposed by Klaus, Hayward, and Song, it is found that the experimental results are not completely identical with the calculated results.

Drive requirements of tractors and communal vehicles are demanding and varied. Energy efficiency and the different requirements in off-road and on-road operation are the basis for a powerful drive. Combinations with the so-called hydrostatic wide angle technology are often used. The article deals with a hydraulic drive with wide angle technology (45°) and an integrated, quick-shift, single stage transmission. A particularly large conversion range can be realized with this. Special shift elements, sensors and an adjustment developed for this purpose enable a fast, quiet and low-wear gear change. This new gearbox development will in future be implemented at RIGITRAC in cooperation with SAUER BIBUS.

The paper describes the design of a prototype vehicle used by Dana Holding Corporation as a mobile laboratory for the development of Spicer® PowerBoost® hydraulic-hybrid powertrain technology. A telehandler vehicle was selected due to its versatility. Starting from the high-level requirements, design choices from the powertrain layout to the control architecture are discussed. The hydraulic-hybrid powertrain system is described, and its performance is analyzed based on representative driving cycles.