Analysis of requirements for valve accuracy and repeatability in high efficiency digital displacement motors

Sondre Nordås, Morten K. Ebbesen, Torben O. Andersen

Research output: Contribution to book/anthology/report/conference proceedingArticle in proceedingResearchpeer-review

Abstract

Traditional variable displacement piston machines achieve high efficiency when operating at high displacements, but struggle with poor efficiency at low displacements. The pistons are connected to high pressure and low pressure in conjunction with the output shaft position and the displacement is changed by changing the piston stroke, resulting in almost constant friction, leakage, and compressibility losses independent of displacement. In digital displacement machines, the rotary valve is replaced by two fast switching on/off valves connected to every cylinder. By controlling the fast switching on/off valves, the cylinders can be controlled individually and friction, leakage and compressibility losses can be minimized resulting in high efficiency even at low displacements. Previous studies have shown that high efficiency digital displacement machines require fast switching valves with high flow capacity and optimal valve timing strategy. When the digital displacement motor is to start, stop or be controlled at low speeds, the on/off valves must be able to open against high pressure difference. When opening the valves actively, the valve timing has to be conducted properly to minimize valve throttling losses and flow and pressure peaks. First, this paper shortly describes a previously developed method to estimate valve characteristics like transition time and flow capacity for a digital displacement machine. Then the paper presents a novel method of describing the required valve accuracy and repeatability to keep the valve throttling losses low and machine efficiency high.
Original languageEnglish
Title of host publicationProceedings of the BATH/ASME 2018 Symposium on Fluid Power and Motion Control
Number of pages11
PublisherAmerican Society of Mechanical Engineers
Publication dateSep 2018
Pages1-11
Article numberFPMC2018-8908
ISBN (Electronic)978-0-7918-5196-8
DOIs
Publication statusPublished - Sep 2018
EventBATH/ASME 2018 Symposium on Fluid Power and Motion Control - Bath, United Kingdom
Duration: 12 Sep 201814 Sep 2018

Conference

ConferenceBATH/ASME 2018 Symposium on Fluid Power and Motion Control
CountryUnited Kingdom
CityBath
Period12/09/201814/09/2018

Keywords

  • motors
  • valves
  • displacement

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