Decentralized Compact Hydraulic Supply through High-Speed Components

  CAD image of the high-speed EHA

One obstacle to the use of electro-hydraulic axes (EHA) on mobile machinery is the power density that has been achievable to date using state-of-the-art technology. A decentralized hydraulic supply combines the advantages of a demand-oriented provision of hydraulic power at the consumer and reduced line losses. To increase the power density, a high-speed internal gear pump for an electro-hydraulic high-speed drive was developed at ifas.

 
Benefit Procedure

Increase of the power density of electro-hydraulic drives through high-speed components

Development of a high-speed internal gear pump

Raising the speed level of hydraulic pumps

Efficiency studies of the internal gear pump

Decentralized EHA for mobile applications

Development of an EHA with high-speed actuator

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Decentralized Compact Hydraulic Supply with High-Speed Components

In mobile machines, such as excavators, the hydraulic power is usually provided by a central pressure supply in the vehicle. This usually consists of one or more pumps. The operator can control the actuators of the working hydraulics with the help of valves. However, part of the hydraulic power is throttled off by the valve control and converted into heat. The hydraulic power is routed to the individual actuators by means of hoses and pipes. This again results in line losses. A demand-based power supply with a variable-speed drive reduces throttling losses. A decentralised arrangement of the power supply, directly at the consumer, minimises the transmission losses in the lines.

Objectives

In this project, a functional model for an electro-hydraulic axis (EHA) with high-speed drive was investigated. A high-speed internal gear pump was developed for this purpose. Raising the speed level increases the already comparatively high power density of the hydraulic system, but also places high demands on the pump and the hydraulic system of the EHA. The aim was to increase the power density and compactness of the electro-hydraulic drive by means of high-speed components and thus making it attractive for use in mobile machinery.

 
 

Numerical Flow Simulation (CFD)

In order to optimize the operating behavior of the pump at high speeds, numerical flow calculations of the internal gear pump, so-called Computational Fluid Dynamics (CFD) simulations, were carried out at ifas.

Goals of the CFD simulation:

  • Understanding flow processes within the pump
  • Optimisation of the pump for high-speed operation
  • Design of the internal gear pump
  CFD Visualization of the Rotating Internal Gear Pump
 
 

High-Speed-Drive

External Gear Pump Section View of the High-Speed Internal Gear Pump

Within the context of this project, the technology of high-speed drives was investigated. For this purpose, an internal gear pump was developed and subsequently tested. The system architecture of the EHA was adapted to the high-speed drive and the application in the field of mobile applications.

 
 

On the left hand side of the image below, the prototype of the high-speed internal gear pump is shown along with the 48 V high-speed motor. The nominal power of the motor is 10 kW. The right hand side of the image shows the volumetric flow and the volumetric efficiency over the rotational speed of the drive. The suction side of the pump (ND) was preloaded and the volumetric flow nearly increases linearly up to the maximal speed of 10000 min-1. Without preloading the suction side a speed of 5500 min-1 could be achieved, which yields an increase of 10% to 50% compared to the state of the art.

  Diagram of volumetric flow and volumetric efficiency over rotational speed Copyright: © ifas
 
 

Electro-Hydraulic Axis (EHA) with High-Speed Drive

Compact Excavator with EHA Copyright: © ifas Compact Excavator with EHA

The functional model of the EHA, including the electro-hydraulic high-speed drive, was mounted and tested on a compact excavator. For this purpose the conventional stick cylinder was replaced by the developed EHA. By testing on the vehicle the feasibility of the decentralized drive concept was demonstrated.

 
 

Acknowledgement

Logo of the BMWi

The IGF Project 19224 N / 1 und 19224 N / 2 of the Forschungsvereinigung Forschungskuratorium Maschinenbau e.V. – FKM, Lyoner Straße 18, 60528 Frankfurt am Main was founded via the AiF as part of the Programme for the Promotion of Joint Industrial Research and Development (IGF) by the Federal Ministry of Economics and Energy based on a resolution of the German Bundestag.

  Copyright: © AIF   Copyright: © FVB
 
 

With the friendly support of

  • TwinMesh by CFX Berlin
  • BAUER Maschinen GmbH
  • Volvo Construction Equipment Germany GmbH
  • Hydac
  • Wilhelm Hoven Maschinenfabrik GmbH & Co
  • Eckerle Technologies GmbH
  • HydraForce
  • Bosch
  Logos of the Supporters Supporters of the Project
 
 

Publications

Schlussbericht Dezentrale kompakte Hydraulikversorgung durch High-Speed-Komponenten
Pietrzyk T. et al.: Design study of a high speed power unit for electro hydraulic actuators (EHA) in mobile applications, 11th International Fluid Power Conference, Aachen, Germany, 19-21 March, 2018, pp. 232-245