Hydraulic Fluid Power: Fundamentals, Applications, and Circuit Design

ISBN-13: 9781119569114 / Angielski / Twarda / 2021 / 704 str.

Andrea Vacca

Spis treści

PART I:Fundamental principles4Objectives4CHAPTER 1:Introduction to hydraulic control technology6Historical perspective7Fluid power symbology and its evolution12Common ISO Symbols16Problems25CHAPTER 2:Hydraulic fluids28Ideal vs. Actual hydraulic fluids28Classification of hydraulic fluids31Mineral oils (H)32Fire resistant fluids (HF)33Synthetic fluids (HS)34Environmentally friendly fluids34Water hydraulics34Comparisons between hydraulic fluids35Physical properties of hydraulic fluids36Fluid compressibility: Bulk ModulusFluid density38Fluid viscosity42Viscosity as a function of temperature43Viscosity as a function of pressure47Entrained air, gas solubility and cavitation48Entrained air48Gas solubility48Equivalent properties of liquid-air mixtures50Contamination in hydraulic fluids57Considerations on hydraulic filters59Filter placement64Considerations on hydraulic reservoirs68Tank volume68Basic design of a tank69Problems71CHAPTER 3:Fundamental Equations73Pascal's law73Basic law of fluid statics74Volumetric flow rate77Conservation of mass80Application to a hydraulic cylinder81Bernoulli's Equation84Generalized Bernoulli's equation85Major losses calculation87Minor losses89Hydraulic resistance90Stationary modeling of flow networks92Momentum equation96Flow forces100Problems106CHAPTER 4(*):Orifice Basics111The orifice equation111Fixed and variable orifices115Power loss in orifices117Parallel and series connection of orifices119Functions of orifices in hydraulic systems123Orifices in pressure and return lines123Orifices in pilot lines126Problems131CHAPTER 5:Dynamic Analysis of Hydraulic Systems134Pressure build-up Equation - hydraulic capacitance134Fluid inertia Equation - hydraulic inductance140Modeling flow network - dynamic considerations146Validity of the lumped parameter approach151Further considerations on the line impedance model152Damping effect of hydraulic accumulators153Problems156References160PART II:Main hydraulic components4Objectives5CHAPTER 6 (**):Hydrostatic pumps and motors6Introduction6The ideal case7General operating principle9ISO symbols13Ideal equations14The real case16Losses in pumps and motors17Fluid compressibility17Internal and external leakage20Friction21Other types of losses23Volumetric and hydro-mechanical efficiency24Trends for volumetric and hydromechanical efficiencies28Design types34Swashplate type axial piston machines35Bent axis type axial piston machines38Radial piston machines39Gear machines40Vane type machines43Problems46CHAPTER 7(*):Hydraulic cylinders50Classification50Cylinder analysis52Ideal vs. real cylinder55Problems61CHAPTER 8(*):Hydraulic control valves63Spring basics64Check and shuttle valves65Check valve65Pilot operated check valve66Shuttle valve67Pressure control valves68Pressure relief valve68Direct acting pressure relief valve68Pilot operated pressure relief valve72Pressure reducing valve75Direct acting pressure reducing relieving valve75Pilot operated pressure reducing valve77Flow control valves80Two-way flow control valve80Fixed displacement pump circuit with a two-way flow control valve83Three-way flow control valve87Fixed displacement pump circuit with a three-way flow control valve89Directional control valves95Meter-in and meter-out configurations97Neutral position100Actuation methods103Servovalves107Characteristic of servovalves112Servovalves vs. proportional valves123Problems126CHAPTER 9(*):Hydraulic Accumulators132Accumulator Types132Weight loaded accumulators132Spring-loaded accumulators132Gas-charged accumulators133Piston-type accumulators133Diaphragm-type accumulators134Bladder-type accumulators135Operation of gas charged accumulators137Typical applications138Energy accumulation138Emergency supply140Energy recuperation140Hydraulic suspensions140Pulsation dampening - shock attenuation141Equations and sizing142Accumulator as energy storage device142Accumulator as dampening device145Problems151References154PART 3:Actuator control concepts3Objectives3CHAPTER 10 (*):Basics of actuator control5Control methods: speed, force and position control5Resistive and overrunning loads7Power flow depending on the load conditions9Problems11CHAPTER 11:General concepts for controlling a single actuator13Supply and control Concepts13Flow supply - primary control18Flow supply - metering control19Flow supply - secondary control21Pressure supply - primary control21Pressure supply - metering control23Pressure supply - secondary control25Additional remarks26CHAPTER 12:Regeneration with single rod actuators27Basic Concept of regeneration27Actual implementation32Directional control valve with external regeneration valves32Directional control valve with regenerative extension position33Solution with automated selection of the regeneration mode34Problems36References38PART 4:Metering controls for a single actuator3Objectives3CHAPTER 13:Fundamentals of metering control5Basic meter-in and meter-out control principles5Meter-in controlExtension with resistive loadsRetraction with overrunning loadsMeter-out control10Extension with resistive loads 14Retraction with overrunning loads18Remarks on meter-in and meter-out controls19Actual metering control components36Single spool proportional DCVs41Independent metering control elements38Usage of anti-cavitation valve for unloaded meter-out51Problems49CHAPTER 14:Load holding and counterbalance valves53Load holding valves53Pilot operated check valve61Counterbalance valves60Basic operating principle67CBV architecture69CBV detailed operation72Effect of the pilot ratio and of the pressure setting83Counterbalance valve with vented spring chambers85Problems78CHAPTER 15:Bleed-off and open center circuits80Bleed-off circuit operation91Energy analysis94Basic open center system97Operation98Open center valve design101Energy analysis102Advanced open center control architectures106Negative flow control106Basic Schematic106Operation107Pump displacement setting mechanism110Positive flow control114Basic Schematic114Operation115Pump displacement setting mechanism115Energy analysis for advanced open center architectures116Problems118CHAPTER 16:Load sensing systems109Basic load sensing control concept121LS system with fixed displacement pump122Basic Schematic122Operation123Energy analysis125Saturation conditions126Load sensing valve127LS system with variable displacement pump137Basic Schematic137Operation138Energy analysis139Saturation conditions140Load sensing pump148LS solution with independent metering valves157Electronic load sensing (E-LS)159Problems162CHAPTER 17:Constant pressure systems150Constant pressure system based on a variable displacement pump163Basic schematic and operation163Energy analysis166Constant pressure system with unloader (CPU)167Constant pressure system based on a fixed displacement pump170Basic schematic and operation170Application to hydraulic braking circuits173Problems175ReferencesPART 5:Metering control of multiple actuators3Objectives3CHAPTER 18:Basics of multiple Actuator Systems5Actuators in series and in parallel5Series configuration6Parallel configuration8Elimination of the load interference in parallel actuators12Solving load interference using compensators12Solving load interference with a volumetric coupling13Syncronization of parallel actuators through flow dividers15Spool type flow divider15Spool type flow divider-combiner16Volumetric flow divider-combiner19Linear flow divider-combiner24Rotary flow divider-combiner25Problems23CHAPTER 19:Constant pressure systems for multiple actuators27Basic concepts for a Multi-user constant pressure system27Basic schematic35Flow saturation36Energy analysis37Complete schematic of a multi-user constant pressure system29Problems33CHAPTER 20:Open center systems for multiple actuators35Parallel open center systems36Operation46Energy analysis48Flow saturation49Considerations on the open center spool design49Opening areas39Opening delay (valve timing)41Load interference in open center systems41Tandem and series open center systems47Tandem configuration60Series configuration63Advanced open center circuit for multiple users: the case of excavators49Problems52CHAPTER 21:Load sensing systems for controlling multiple actuators53Load sensing system without pressure compensation (LS)53Basic circuit69Energy analysis72Valve implementation and extension to more actuators74Load sensing pressure compensated systems (LSPC)61LSPC with pre-compensated valve technology61Basic circuit79Energy analysis82Valve implementation and architecture84LSPC with post-compensated valve technology70Basic circuit90Energy analysis92Valve implementation and architecture94Flow saturation and flow sharing in LS systems79Flow saturation with pre-compensated LSPC80Flow saturation with post-compensated LSPC82Pre vs. post compensated comparison84Independent metering systems with load sensing88Problems91CHAPTER 22:Power steering and hydraulic systems with priority function102Hydraulic power steering103Classification of hydraulic power steering systems103Hydrostatic power steering111Hydrostatic steering unit description114Types of hydrostatic steering units119Priority valves121Priority valve for a fixed displacement flow supply121Priority valve for load sensing circuits128Problems131ReferencesPART 6:Hydrostatic transmissions and hydrostatic actuators3Objectives5CHAPTER 23:Basics and classifications6Hydrostatic transmissions and hydrostatic actuators6Basic definitions6Supply concepts used in HTs and HAs9Primary units for hydrostatic transmissions and actuators10Constant speed prime mover and variable displacement pump10Variable speed prime mover and fixed displacement pump10Variable speed prime mover and variable displacement pump11Over-center variable displacement pump11Typical applications12CHAPTER 24:Hydrostatic transmissions15Main parameters of a hydrostatic transmission15Theoretical layouts19Pump and motor with fixed displacement (PFMF)19Variable displacement pump and fixed displacement motor (PVMF)20Fixed displacement pump and variable displacement motor (PFMV)21Variable displacement pump and variable displacement motor (PVMV)23Variable displacement pump and dual displacement motor (PVM2)25Open circuit hydrostatic transmissions29Open-circuit HT with flow supply: basic circuit29Open circuit HT with flow supply: common implementation31Open circuit displacement regulator33Open circuit HTs with pressure supply35Closed circuit hydrostatic transmissions40Charge circuit and filtration41Cross-port relief valves45Flushing circuit47Closed circuit displacement regulators54Electro-hydraulic displacement regulator for closed circuit pumps54Automotive control for closed circuit pumps56Conceptual schematic58Actual implementation60Electro-hydraulic displacement regulator for motors59Automatic pressure regulator for motors60Problems61CHAPTER 25:Hydrostatic transmissions applied to vehicle propulsion67Basic of vehicle transmission67Classification for variable ratio transmission systems71Power-split transmissions74Planetary gear train76Hydromechanical power split transmission78Analysis of an output coupled hydromechanical power split transmissionAnalysis of an input coupled hydromechanical power split transmissionHybrid transmissions92Series hybrids93Parallel hybrids95Series-parallel hybrids (or power split hybrids)97Sizing hydrostatic transmissions for propel applications100Step 1: Maximum tractive effort calculation101Step 2: Fixed or variable displacement motor selection102Step 3: Sizing of the motor (secondary unit)104Step 4: Sizing of the pump (primary unit)105Step 5: Check results106Problems112CHAPTER 26:Hydrostatic actuators113Open circuit hydrostatic actuators113Closed circuit hydrostatic actuators116Cylinder extension117Extension in pumping mode117Extension in motoring mode118Cylinder retraction120Retraction in motoring mode121Retraction in pumping mode122Further considerations on the charge pump and the accumulator124Final remarks on hydrostatic actuators127CHAPTER 27:Secondary controlled hydrostatic transmissions129Secondary control circuit with tachometric pump132Secondary control circuit with tachometric pump and internal force feedback135Secondary control circuit with electronic control137Multiple actuators139ReferencesAPPENDIX 1 - Prime movers and their interaction with the hydraulic circuitObjectivesCorner power method and its limitationsDiesel engine and its interaction with a hydraulic pumpDiesel engine regulationEngine stallOverrunning loadsFuel consumptionElectric prime moversBrushed DC electric motorsDC hydraulic power unitsInduction motors (or asynchronous motor)Synchronous motorPower limitation in hydraulic pumpsTorque limiting using fixed displacement pumpsTorque limiting using variable displacement pumpsReferences

O autorze

ANDREA VACCA is the Maha Chair for Fluid Power Systems at Purdue University and he leads Purdue's Maha Fluid Power Research Center. He obtained his MSc at the University of Parma and his doctorate in Energy Systems at the University of Florence. He has written over 150 technical papers on fluid power technology and was awarded the 2019 Joseph Bramah Medal by the Institution of Mechanical Engineers for contributions to fluid power research.GERMANO FRANZONI obtained his Ph.D. in mechanical engineering in 2006 from the University of Parma, Italy. Since then, he has worked in the Hydraulics Industry, both in Europe and USA. He is currently part of the Mobile Systems Engineering team for North America at Parker Hannifin. He specializes in systems design, business development and R&D. He works side by side with the major OEMs in the construction, mining, vocational truck and military markets. He holds two patents and has several patent pending applications. He is author of several scientific papers and has presented at various fluid power conferences and symposia.