كتاب Basics of Hydraulic Systems

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Basics of Hydraulic Systems
Second Edition
By
Qin Zhang

و المحتوى كما يلي :

Table of Contents
Preface ix
Preface to the Second Edition .xi
About the Author xiii
1. Introduction to Hydraulic Power .1
1.1 Power Transmission and Hydraulic Systems 1
1.1.1 Power Transmission in Machinery Systems 1
1.1.2 Hydraulic Power Systems on Mobile Equipment 2
1.1.3 Hydraulic Components and System Schematics .4
1.2 Fundamentals of Hydraulic Power Transmission 6
1.2.1 Multiplication of Force 6
1.2.2 Conservation of Energy 8
1.2.3 Continuity of Fluids 11
1.3 Energy and Power in Hydraulic Systems 12
1.3.1 Energy Conversion in Hydraulic Systems 12
1.3.2 Hydraulic Power and Efficiency 13
1.4 Standard Graphical Symbols for Hydraulic System Schematics 15
1.5 Units and Unit Conversion in Hydraulic Systems . 18
References .21
Exercises 22
2. Hydraulic Power Generation 25
2.1 Hydraulic Pumps 25
2.1.1 Overview of Hydraulic Pumps 25
2.1.2 Principle of Positive Displacement Pumping 26
2.1.3 Gear Pumps 27
2.1.4 Vane Pumps 32
2.1.5 Piston Pumps 34
2.2 Control of Hydraulic Power Generation 41
2.2.1 Corner Power and Pump Efficiency 41
2.2.2 Pressure Limiting 45
2.2.3 Load Sensing with Pressure Limiting 47
2.2.4 Torque Limiting .48
References .51
Exercises 52
3. Hydraulic Power Distribution .55
3.1 Hydraulic Control Valves .55
3.1.1 Overview of Hydraulic Valves .55
3.1.2 Fundamentals of Valve Control .57
3.1.3 Pressure Control Valves 64
3.1.4 Directional Control Valves .71
3.1.5 Flow Control Valves . 76vi Table of Contents
3.1.6 Electrohydraulic Control Valves 81
3.1.7 Programmable Electrohydraulic Valves .87
3.1.8 Select Appropriate Control Valves 89
3.2 Hydraulic Manifolds 91
3.2.1 Overview of Hydraulic Manifolds 91
3.2.2 Modular-Block Manifolds . 91
3.2.3 Single-Piece Hydraulic Manifolds . 91
3.3 Hydraulic Lines .93
3.3.1 Major Components of Hydraulic lines 93
3.3.2 Hydraulic Hoses .93
3.3.3 Metal Tubes and Pipes 96
3.3.4 Designing Hydraulic Lines 98
3.3.5 Hose Routing and Installations . 101
3.4 Energy Losses and Heat Generation in Power Distribution . 103
References .105
Exercises 107
4. Hydraulic Power Deployment 109
4.1 Hydraulic Power Deployment Components . 109
4.1.1 Hydraulic Actuators 109
4.1.2 Principle of Hydraulic Actuating 109
4.2 Hydraulic Cylinders . 113
4.2.1 Classification of Hydraulic Cylinders . 113
4.2.2 Operating Parameters of Hydraulic Cylinders 114
4.2.3 Hydraulic Cylinder Cushions 120
4.2.4 Hydraulic Cylinder Power Transmission . 121
4.2.5 Hydraulic Cylinder Applications 123
4.3 Hydraulic Motors 126
4.3.1 Classification of Hydraulic Motors 126
4.3.2 Operating Parameters of Hydraulic Motors 126
4.3.3 High-Speed Hydraulic Motors . 129
4.3.4 Low-Speed High-Torque Motors . 135
4.3.5 Oscillating Rotary Actuators . 138
4.3.6 Speed Control and Power Transmission of Hydraulic Motors . 140
4.4 Hydrostatic Transmission 146
4.4.1 Overview of Hydrostatic Transmission 146
4.4.2 Configurations of Hydrostatic Transmission 148
4.4.3 Control of Hydrostatic Transmission 153
4.4.4 Applications of Hydrostatic Transmission . 159
References .163
Exercises 164
5. Hydraulic Power Regulation 167
5.1 Overview of Power Regulation . 167
5.1.1 Regulating Hydraulic Power 167
5.1.2 Commonly Used Power-Regulating devices . 168
5.2 Power-Absorbing Devices 170
5.2.1 Hydraulic Shock Absorbers 170
5.2.2 Hydraulic Fluid Springs 173Table of Contents vii
5.3 Power Storage Devices . 176
5.3.1 Functions of Hydraulic Accumulators 176
5.3.2 Operation Principles of Hydraulic Accumulators 178
5.3.3 Sizing Hydraulic Accumulators 181
5.3.4 Mounting Hydraulic Accumulators 183
5.4 Power Regeneration Devices . 185
5.4.1 Functions of Hydraulic Power Regeneration . 185
5.4.2 Hydraulic Pressure Intensifiers . 186
5.4.3 Two-Speed Hydraulic Cylinders . 188
5.4.4 Hydraulic braking chargers . 189
References .191
Exercises 192
6. Hydraulic Fluids and Fluid-Handling Components . 195
6.1 Hydraulic Fluids 195
6.1.1 Functions of Hydraulic Fluids . 195
6.1.2 Hydraulic Fluid Properties . 196
6.1.3 Types of Hydraulic Fluids 200
6.2 Hydraulic Fluids Reservoirs 202
6.2.1 Functionality of Fluid Reservoirs 202
6.2.2 Fluid Reservoir Components .203
6.2.3 Fluid Reservoir Sizing .206
6.3 Hydraulic Fluid Filters .208
6.3.1 Hydraulic Fluid Contamination 208
6.3.2 Fluid Cleanliness Measurements 210
6.3.3 Hydraulic Fluid Filters 211
6.4 Other Components 215
6.4.1 Heat Exchangers 215
6.4.2 Seals . 218
References .221
Exercises 221
7.
Hydraulic Circuits 223
7.1 Basic Circuits .223
7.1.1 Pressure Control Circuits .223
7.1.2 Direction Control Circuits 227
7.1.3 Speed Control Circuits 228
7.1.4 Sequencing Control Circuits 233
7.1.5 Synchronizing Control Circuits .234
7.2 Special Function Circuits .234
7.2.1 Pump-Unloading Circuits 235
7.2.2 Cylinder Pressure-Holding Circuits .236
7.2.3 Hydraulic Motors Series-Parallel Circuits 236
7.2.4 Hydraulic Braking Circuits 237
7.2.5 Accumulator Circuits 238
7.2.6 Replenishing and Cooling Circuits . 239
7.2.7 Hydraulic Filtering Circuits . 240
7.3 Integrated Hydraulic Circuits . 240
7.3.1 Hydrostatic Transmission Circuits 240viii Table of Contents
7.3.2 Multibranch Integrated Hydraulic Circuits .244
7.3.3 Programmable Electrohydraulic Circuits 247
References .249
Exercises 249
8. Hydraulic Systems Modeling .253
8.1 Mathematical Model of Hydraulic Systems 253
8.1.1 Building Blocks of Hydraulic System Modeling .253
8.1.2 Model of Simplified Valve-Controlled Systems 257
8.2 System Analysis 261
8.2.1 System Block Diagram and Transfer Function 261
8.2.2 Transfer Function Simplification .266
8.2.3 System State-Space Equations 268
8.2.4 System Performance Characteristics . 269
References .273
Exercises 273
9. Electrohydraulic Systems Control .277
9.1 Concepts of Electrohydraulic System Control 277
9.1.1 Basic Concept of Automatic Controls .277
9.1.2 Open- and Closed-Loop Controls . 278
9.1.3 Transient Response and Steady-State Error . 279
9.1.4 Gain and Feedback 281
9.1.5 Frequency Response and the Bode Diagram .283
9.2 Hydraulic Velocity, Position, and Force Controls .285
9.2.1 Proportional and Servo Actuation in Electrohydraulic
Control Valves 285
9.2.2 Velocity Controls 287
9.2.3 Position Controls 289
9.2.4 Force Controls .289
9.3 Basic Methods for Electrohydraulic System Controls 290
9.3.1 Bang-Bang Control .290
9.3.2 Modulated Feedforward Control 291
9.3.3 PID Control . 292
9.3.4 A Few Other Control Methods 293
References .294
Exercises 295
Appendix A: Hydraulic Power Formulas 299
Appendix B: Orifice Area Formulas of a Few Typical Shaped Orifices .303
Appendix C: Some Useful Conversion Factors 305
Appendix D: Solutions to Selected Exercise Problems 307
Index .
311
Index
Note: Italicized page numbers refer to figures,
bold page numbers refer to tables.
A
Absolute viscosity, 197
Accumulator circuits, 238–239, 239
Accumulators
adiabatic discharging, 182
as auxiliary power source, 176
characteristic states, 180
charging stage, 180
defined, 169, 176
discharging stage, 180
drained stage, 180
empty stage, 180
flow rates, 181
fluid volume insensitive, 178
functions of, 176–177
gas-loaded, 179
isothermal discharging, 181
as leakage makeup source, 177
mounting, 183–184
operation principles of, 178–181
precharged stage, 180
precharged volume, 180
as pulsation absorber, 176
response times, 180
as shock damper, 177
six-stage operating principles, 180
sizing, 181–183, 184–185
spring-loaded, 178–179
as thermal expansion compensator, 177
total volume, 180
weight-loaded, 178
Active zones, 62
Actual output torque, 127
Actuating cylinders, 119
Actuating piston, 186
Actuating pockets, 131
Actuators
capacity, 112–113
defined, 109
linear, 109
oscillating rotary, 138–140
principles of, 109–113
rotary, 109
softness, 109
Addendum circles, 27–28
Adiabatic discharging, 182
Air contamination, 209
Air-dissolving rate, 199
All-metal fittings, 97
American National Standards Institute
(ANSI), 5, 15
Antifoaming, 199
Antiwear performance, 198
A-port, 73–74
Area, 6
Area ratio, 114
Armature, 82
Automatic control, 277
Automatic direction switching circuits, 227
Automobile transmission fluids, 200
Average current, 83
Axial-piston motors, 134–135
Axial-piston pumps, 34, 35
B
Baffling device, 204–205, 205
Balanced vane motors, 131–132
Balanced vane pumps, 33
Balancing circuits, 226
Ball valves, orifice area of, 303
Bang-bang control, 285, 290–291
Bayonet, 96
Bent angle, 36
Bent-axis piston motors, 134
Bent-axis pump, 36
Bernoulli’s equation, 9–10, 172
Beta ratio, 212
Bidirectional motors, 126
Biodegradeable fluids, 100
Black box, 261
Bleed-off circuits, 229
Bleed-recharge circuit, 226–227, 227
Block diagram, 261–266
of basic feedback control system, 281
of basic modulated feedforward control
systems, 291
Block diagram transformations, 262,
263–264
Bode diagram, 283–285
Bode plot, 283
Boosting piston, 186312 Index
Boundary lubrication, 195
Breakaway force, 122
Breakaway torque, 127
Breather cap, 204
British unit system, 18
Buckling effect, 97
Bulk modulus, 198
C
Cam-lock couplings, 96
Cam ring, 32
Cam-type radial-piston motors, 135
Cap end, 109
Cartridge valve, 55
Check valves, 72
Chemical contamination, 209–210
Circuits, 223–249
accumulator, 238–239, 239
basic, 223
cylinder-pressure holding, 236
direction control, 227–228
hydraulic braking, 237–238, 238
hydraulic filtering, 240
hydraulic motors series-parallel,
236–237, 237
integrated hydraulic, 240–249
pressure control, 223–227
pump-unloading, 235–236, 235
replenishing and cooling, 239
sequencing control, 233–234
special function, 234–240
speed control, 228–233
synchronizing control, 234
Circular cylinder rotor, 132
Closed-center speed control circuits, 231
Closed-center valve, 74, 87
Closed circuits, 151–152
Closed-loop closed-circuit HST, 154–155, 154
Closed-loop controls, 278–279, 279
Closed-loop system analysis, 284–285
Closed-relief valve, 152
Commutator, 131
Compound hydraulic springs, 174
Conduct lines, 16
Constant power control, 50
Constant-power transmissions, 146
Constant-pressure-reducing control, 67–68
Constant-torque HST, 243
Constant-torque transmissions, 146
Constant velocity force, 122
Continuous feedback, 291
Continuous rotation motors, 126
Control valves, 57–90
central (neutral) position, 60
directional, 71–76
electrohydraulic, 81–87
flow control valves, 76–80
hydraulic orifice, 57
hydraulic resistance, 57
orifice area, 57
pressure control valves, 64–71
selecting, 89–90
Conversion factors, 305–306
energy, 305
force, 305
gravity, 306
mass, 306
power, 305
pressure, 306
torque, 306
velocity, 306
volume, 305
Cooling circuits, 239
Cooling fan, 206
Corner power, 42, 153–154
Corrosion prevention, 199
Counterbalance valves, 69–70, 70
Cracking points, 62
Cracking pressure, 64
Critically damped system, 280
Cubic centimeters (cc) per revolution, 126
Cubic inches per revolution, 126
Cushion(s), 120–121
pressure, 121
velocity, 121
Cylinder-pressure holding circuits, 236
Cylinders, 113–126
applications, 123–126
area ratio, 114
body, 113
classification, 113–114
components of, 113
cushions, 120–121
defined, 109
differential extension, 115
double-rod, 116, 116
extension cycle, 114
extension operation, 109
hydraulic stiffness of, 268
natural frequency of, 111
operating parameters, 114–119
in parallel systems, 124–126
power transmission, 121–123
ram, 116–117, 117
retraction cycle, 114Index 313
retraction operation, 109
single-acting, 116
single-rod double-action cylinder, 109, 113
speed, 299
spring-return single-acting, 116
stiffness of, 109
telescopic, 117–118, 117
two-speed, 169, 188–189
D
Damper, 253
Deadband, 89–90, 270
Dead zones, 62
Dedendum circles, 27–28
Dial adjustment approach, 143
Differential equation, second-order, 255
Differential extension, 115
Diffusers, 205
Direct-acting relief valves, 64–65
Direct drive gerotor motor, 130
Directing states, 73
Directional control valves, 16, 71–76,
285–286
Direction control circuits, 227–228
Discrete feedback, 290
Disk valves, orifice area of, 303
Displacement, 7
Double-acting intensifiers, 187–188
Double-rod cylinder. See also Cylinders
configuration of, 116
defined, 116
system load, 272
Double shutoff lock-ball-type coupling, 95
Double-vane actuators, 139
Drilled-type manifolds, 92
Dual gain, 90
Dual-parameter control, 48
Dynamic resistance, 127
E
Effective bulk modulus, 198
Effective current, 83
Efficiency, 13–14
hydraulic power and, 13–14
mechanical, 43, 112, 127
motor, 14–15
overall, 112, 129
power, 43
pump, 14, 43
spool valve, 260–261
stall torque, 112, 155
torque, 44
volumetric, 43, 112, 128
Electrical power transmission, 1–2
Electrohydraulic control valves, 81–87
electromechanical drivers for, 81
on-off, 81
programmable, 87–88, 88
proportional, 81
solenoid-controlled pilot-operating design,
84–85, 85
solenoid drivers, 81–83
Electrohydraulic systems control, 277–294
automatic control, 277
bang-bang control, 285, 290–291
basic methods for, 290–294
Bode diagram, 283–285
closed-loop controls, 278–279, 279
concepts of, 277–285
continuous feedback, 291
critically damped system, 280
directional control valves, 285–286
discrete feedback, 290
feedback, 281–282, 282
feedforward controls, 279, 279, 291
feedforward-plus-PID control, 293–294
force controls, 289–290
frequency response, 283–285
gain, 280
gain-scheduling control, 291–292
modulated feedforward control, 291
open-loop controls, 278–279, 279
overdamped system, 280
overshoot, 279–280
PID control, 292–293
position controls, 289
proportional and servo actuation in, 285–287
proportional control valves, 285–286
response time, 280
rise time, 279–280
schematics of, 278
servo control valves, 285–286
settling time, 279
solenoid control valves, 286
steady-state error, 279–281
transient response, 279–281
underdamped system, 280
velocity controls, 287–288
Electronic control unit, 158
Energy, conversion factors, 305
Energy conservation, 8–11
law, 172
method, 158
Energy conversion, 12–13314 Index
Energy loss, 103–105, 158
English unit system, 18
Entrained air, 199, 209
Exhaust pockets, 131
Extension cycle, 114
Extension operation, 109
External gear motor, 129
External-gear pumps, 27
External power regenerators, 185
F
Fabric-reinforced hoses, 93
Feedback, 281–282, 282
Feedforward controls, 279, 291
Feedforward-plus-PID control, 293–294
Filler cap, 204
Filters, 211–215
circuits, 240
dirt-holding capacity, 214
efficiency, 212–213
high-pressure, 211
low-pressure, 211
ratings, 212, 214–215
Fire-resistant hydraulic fluids, 201
Fitting nut, 97
Fixed-displacement motor, 241
Fixed-displacement pumps, 16, 33, 241
Fixed-pressure-reducing control, 68
Fixed pump-fixed motor HST, 148, 241–242
Fixed pump-variable motor HST, 149, 241
Flared fittings, 97
Flareless fittings, 98
Flat-face couplings, 95
Float-center valve, 75, 87
Flow capacity, 62, 291
Flow continuity, 255, 257
Flow control orifice, 255
Flow control orifice equation, 256
Flow control valves, 16
flow-dividing, 79–80
noncompensation, 77
pressure-compensated, 78–79
Flow dividers, 79–80
Flow-dividing control valves, 79–80
Flow gain, 62–63
Flow-passing rate, 90
Flow-sensing control, 46–47
Flow variation index, 28
Flow velocity angle, 60
Fluid continuity, 11–12, 172
Fluid density, 196
Fluid-level gauge, 205
Fluid power transmission, 2
Fluid reservoirs, 202–207
capacity, 206
components of, 203–206
configuration of, 203
dimension, 206
functionality, 202–203
material, 206
sizing, 206–207
Fluid subsystem, 253
Force, 6
conversion, 255, 256
conversion factors, 305
multiplication of, 6–8
Force controls, force controls, 289–290
Forced-open check valves, 72
Force motor, 81
Formulas, 299–301
hydraulic cylinder speed, 299
hydraulic force in cylinder, 300
hydraulic power, 301
hydraulic pump/motor speed, 299–300
hydraulic torque in pump and motor, 300
mechanical power in cylinders, 301
mechanical power in pump or motor, 301
Newton’s law of motion, 299
orifice equation, 300
Pascal’s law of pressure, 299
Four-way three-position valve, 74
Free air, 209
Free-piston assembly, 119
Free water, 209
Frequency response, 283–285
Full-film lubrication, 195
Full-flow pressure, 64
G
Gain, 281–282
Gain-scheduling control, 291–292
Gas contamination, 209
Gas-loaded accumulators, 179
Gear motors, 129
Gear pumps, 27–32. See also Pump(s)
addendum circles, 27–28
dedendum circles, 27–28
external, 27
flow variation index, 29
internal, 27
mesh overlap index, 29
theoretical flow rate, 31
volumetric displacement, 31
volumetric efficiency, 31–32Index 315
Gerotor pumps, 31
Gravity, conversion factors, 306
H
Head end, 109
Heat contamination, 209
Heat exchangers, 215–218
Heat generation, 103–105
High-pressure filters, 211
High-speed state, 119
Hose connectors, 95
Hose fittings, 95
Hoses, 93–96
connectors, 95
fittings, 95
hydraulic hoses, 93–96
inside diameter, 93
leak-free connections, 100
outside diameter, 93
polytetrafluoroethylene (PTFE), 93–94
routing and installations, 101–103, 102
sizing, 101
Hydraulic accumulators
adiabatic discharging, 182
as auxiliary power source, 176
characteristic states, 180
charging stage, 180
defined, 169, 176
discharging stage, 180
drained stage, 180
empty stage, 180
flow rates, 181
fluid volume insensitive, 178
functions of, 176–177
gas-loaded, 179
isothermal discharging, 181
as leakage makeup source, 177
mounting, 183–184
operation principles of, 178–181
precharged stage, 180
precharged volume, 180
as pulsation absorber, 176
response times, 180
as shock damper, 177
six-stage operating principles, 180
sizing, 181–183, 184–185
spring-loaded, 178–179
as thermal expansion compensator, 177
total volume, 180
weight-loaded, 178
Hydraulic actuators
capacity, 112–113
defined, 109
linear, 109
oscillating rotary, 138–140
principles of, 109–113
rotary, 109
softness, 109
Hydraulic braking chargers, 189–190
Hydraulic braking circuits, 237–238, 238
Hydraulic circuits, 223–249
accumulator, 238–239, 239
basic, 223
cylinder-pressure holding, 236
direction control, 227–228
hydraulic braking, 237–238, 238
hydraulic filtering, 240
hydraulic motors series-parallel,
236–237, 237
integrated hydraulic, 240–249
pressure control, 223–227
pump-unloading, 235–236, 235
replenishing and cooling, 239
sequencing control, 233–234
special function, 234–240
speed control, 228–233
synchronizing control, 234
Hydraulic control valves, 55–90, 57–90
central (neutral) position, 60
directional, 71–76
electrohydraulic, 81–87
flow control valves, 76–80
hydraulic orifice, 57
hydraulic resistance, 57
orifice area, 57
overview, 55–57
pressure control valves, 64–71
selecting, 89–90
Hydraulic cylinders, 113–126
applications, 123–126
area ratio, 114
classification, 113–114
components of, 113
cushions, 120–121
defined, 109
differential extension, 115
double-rod, 116, 116
extension cycle, 114
extension operation, 109
natural frequency of, 111
operating parameters, 114–119
in parallel systems, 124–126
power transmission, 121–123
ram, 116–117, 117
retraction cycle, 114316 Index
retraction operation, 109
single-acting, 116
single-rod double-action cylinder, 109, 113
speed, 299
spring-return single-acting, 116
stiffness of, 109
telescopic, 117–118, 117
Hydraulic damping ratio, 268
Hydraulic energy storage devices, 167
Hydraulic fluids, 195–202
antifoaming property of, 199
antiwear performance, 198
bulk modulus, 198
cleanliness, 210–211
contamination of, 208–210
demulsibility of, 199
density, 196
dissolved gases in, 195
dynamic viscosity (absolute viscosity), 197
effective bulk modulus, 198
environmentally safe, 200
filters, 211–215
fire-resistant, 201
fluid density, 196
fluid incompressibility, 109
functions of, 195–196
incompressible, 195
kinematic viscosity, 197
lubricity, 198
operating temperature, 199, 199–200
oxidation stability of, 199
petroleum-based, 200
properties of, 196–200
relative density (specific gravity), 197
reservoirs, 202–207
rust and corrosion prevention, 199
saturation level, 209
seal compatibility of, 200
synthetic-based fire-resistant, 201
thermal stability of, 199
types of, 200–202
viscosity index, 197
water-based, 201–202
Hydraulic fluid springs, 173–175
compound, 174
defined, 169
simple orifice type, 173
tension type, 174
Hydraulic force in cylinder, 300
Hydraulic hoses, 93–96
connectors, 95
fittings, 95
hydraulic hoses, 93–96
inside diameter, 93
leak-free connections, 100
outside diameter, 93
polytetrafluoroethylene (PTFE), 93–94
routing and installations, 101–103, 102
sizing, 101
Hydraulic jack, 6–7
Hydraulic lines, 93–103
components of, 93
designing, 98–101
hydraulic pipes and tubings, 93
metal tubes and pipes, 96–98
Hydraulic manifolds, 91–92
drilled-type, 92
laminar-type, 92
modular-block, 91
single-piece, 91–92
Hydraulic motors, 126–146
classification of, 126
defined, 109, 111
high-speed, 129–135
load-limit function, 112
low-speed high-torque motors, 135–138
operating parameters, 126–129
overall efficiency, 129
piston-type, 133–135
power transmission, 140–145
rolling-vane, 135, 136
sizing of, 145–146
speed control, 140–145
Hydraulic motors series-parallel circuits,
236–237, 237
Hydraulic orifice, 57
Hydraulic power
calculating, 13–14
defined, 14, 145
efficiency and, 13–14
formula, 301
Hydraulic power deployment, 109–163
actuators, 109–113
components, 109–113
cylinders, 113–126
hydrostatic transmission, 146–163
motors, 126–146
Hydraulic power formulas, 299–301
hydraulic cylinder speed, 299
hydraulic force in cylinder, 300
hydraulic power, 301
hydraulic pump/motor speed, 299–300
hydraulic torque in pump and motor, 300
mechanical power in cylinders, 301
mechanical power in pump or motor, 301
Newton’s law of motion, 299Index 317
orifice equation, 300
Pascal’s law of pressure, 299
Hydraulic power generation
control of, 41–50
corner power, 42
load-sensing control, 47–48
power regeneration devices, 185–191
pressure limiting, 42
pressure-limiting compensation, 45–47
pump efficiency, 41–45
speed-boosting, 190–191
torque limiting, 48–50
Hydraulic power regulation, 167–191
devices, 168–169
overview, 167–168
power-absorbing devices, 170–175
power storage devices, 176–185
Hydraulic power systems, 2
geometric shape formation, 4
on mobile equipment, 2–4
power-to-weight ratio, 4
system schematics, 4–5, 5
Hydraulic power transmission, 6–12
energy conservation, 8–11
fluid continuity, 11–12
force multiplication, 6–8
hydraulic fluids and, 195
Hydraulic pressure intensifiers, 186–188
double-acting, 187–188
single-acting, 187
Hydraulic pumps, 25–41
gear pumps, 27–32
maximum speed, 25
minimum speed, 25
overview, 25–26
piston pumps, 34–41
positive displacement pumping, 26–27, 26
rated speed, 25
speed, 299–300
vane pumps, 32–34
Hydraulic resistance, 57
Hydraulic shock absorbers, 170–173
annular clearance type, 170
configurations of, 170, 171
defined, 169
multiple-orifice type, 170
operations, 175
orivis type clearance type, 170
simple orifice type, 170
spear-type, 170
stepped spear type, 170
tapered spear type, 170
Hydraulic springs, 167
Hydraulic stiffness, 266–267
Hydraulic systems
components of, 4–6
electrohydraulic systems control, 277–294
energy and power in, 12–15
energy conversion in, 12–13
graphical symbols, 15–18
hydraulic circuits, 223–249
hydraulic fluids, 195–221
hydraulic power deployment, 109–163
hydraulic power distribution, 55–105
hydraulic power generation, 25–50
hydraulic power regulation, 167–191
mobile equipment, 2–4
modeling, 253–272
power transmission, 1–2, 6–12
system schematics, 4–6
units and units conversion in, 18–20
Hydraulic systems modeling, 253–272
building blocks, 253–257
fluid subsystem, 253
mathematical models, 253–272
mechanical subsystem, 253
simplified valve-controlled systems, 257–261
system analysis, 261–272
Hydraulic torque in pump and motor, 300
Hydrodynamic sealing, 30
Hydrostatic pumps, 25–26, 27
Hydrostatic transmission (HST), 146–163
advantages of, 146
all-wheel drive, 161
applications of, 159–163
base speed, 163
circuits, 240–244
closed circuits, 151
closed-loop closed-circuit, 154–155, 154
configurations, 148–153
constant-torque, 243
control of, 153–158
critical speed, 151
defined, 146
fixed pump-fixed motor, 148, 241–242
fixed pump-variable motor, 149, 241
inline configuration, 159–160, 159
mass, 156
natural frequency of, 155
open circuits, 151
open-loop closed-circuit, 153
open-loop open-circuit, 156
overview, 146–147
pump-to-motor passages, 157
pump-to-pump passages, 157
response time, 153318 Index
split configuration, 160–161, 160
split-torque power transmission, 162
stiffness of, 155
torque-to-speed ratio, 151
variable pump-fixed motor, 148–149, 241
variable pump-variable motor, 149–151, 242
Hysteresis, 63
I
Ice crystals, 209
Ideas gas law, 179
Incompressible fluids, 195
Inline axial-piston motors, 134
Inline-piston pumps, 34, 35
Inner tubes, 93
Inside diameter, 93, 99
Integrated hydraulic circuits, 240–249
hydrostatic transmission circuits, 240–244
multibranch, 244–247
programmable electrohydraulic
circuits, 247–249
Internal gear motor, 129
Internal-gear pumps, 27
Internal leakage, 30
Internal power regenerators, 185
Internal temperature gauge, 206
International Standards Organization (ISO),
5, 15, 197, 210–211
Inverse valve transform, 291
Inverse water solubility, 201
Isothermal discharging, 181
J
Joint Industrial Council (JIC), 15, 202
K
Kinematic viscosity, 197
Kinetic energy, 255
L
Laminar-type manifolds, 92
Laplace transform, 262
Leak-proof seal, 98
Limited rotation motor, 126
Linear actuators, 109
Linear differential equation, 262
Linear displacement transducer (LDT), 291
Linear system, 253
Linear variable differential transformer (LVDT), 89
Line-relief circuit, 223, 224
Live swivel, 103
Load, 7
Load area, 258
Load flow rate, 258
Load-limit function, 112
Load pressure, 258
Load-sensitive system, 245
Lobe pumps, 31
Low-pressure filters, 211
Low-speed high-torque motors, 135–138
Lubrication, 195
Lubricity, 198
M
Magnetic drain plug, 205
Main lines, 16
Main relief, 65–66
Manifolds, 91–92
blocks, 55
drilled-type, 92
laminar-type, 92
modular-block, 91
single-piece, 91–92
Margin pressure, 25, 47
Mass, 253
conversion factors, 306
Mass flow rate, 77
Maximum discharge pressure, 25
Maximum flow velocity, 99
Maximum inlet pressure, 25
Maximum motor speed, 128
Mechanical efficiency, 43, 112, 127
Mechanical power, 14
in cylinders, 301
in pump or motor, 301
Mechanical power transmission, 1
Mechanical subsystem, 253, 255
Mesh overlap index, 29
Metal tubes and pipes, 96–98
Meter-in, 77
Meter-in circuits, 229
Metering control, 57
Metering notches, 57
Metering point power, 42
Meter-out, 77
Meter-out circuits, 229
Microbial contamination, 210
Minimum discharge pressure, 25
Minimum motor speed, 128
Mobile equipment
hydraulic power systems in, 2–4
hydraulic steering system, 4
Modeling, 253–272
building blocks, 253–257Index 319
fluid subsystem, 253
mathematical models, 253–272
mechanical subsystem, 253
simplified valve-controlled systems, 257–261
system analysis, 261–272
Modular-block manifolds, 91
Modulated control, 291
Modulating gain, 270
Modulating zones, 62
Modulation gains, 291
Modulation sensitivity, 62, 83
Moisture-removing filters, 204, 204
Motor(s), 126–146
classification of, 126
defined, 109, 111, 126
displacement, 126
efficiency, 14–15
fixed-displacement, 241
high-speed, 129, 129–135
hydraulic, 111
internal leakage, 112
load-limit function, 112
low-speed high-torque motors, 135–138
maximum speed, 128
mechanical efficiency of, 112
minimum speed, 128
operating parameters, 126–129
oscillating, 111
overall efficiency, 112, 129
piston-type, 133–135
power transmission, 140–145
pump-controlled, 240
rolling-vane, 135, 136
sizing of, 145–146
slippage of, 128
speed control, 140–145
stall, 112
variable-displacement, 241–242
volumetric efficiency of, 112
Multibranch integrated hydraulic circuits, 244–247
load-sensitive system, 245
multipressure setting circuit, 245
prioritized, 244
priority function, 245
Multipressure setting circuit, 245
N
National Aeronautics and Space
Administration (NASA), 210
National Fluid Power Association
(NFPA), 5, 202
National Institute of Standards and Technology
(NIST), 210
Natural frequency, 267
Needle valves, 77
orifice area of, 303
Newtonian shear stress equation, 197
Newton’s law of motion, 299
Newton’s second law of motion, 172
Noncompensation flow control valves, 77
Nonlinear valves, 63
No-spill couplings, 96
O
Oil-in-water emulsion, 202
On-off control valves, 81
Open-center speed control circuits, 230
Open-center valve, 74–75, 87
Open circuits, 151
Open-loop closed-circuit HST, 153
Open-loop controls, 278–279, 279
Open-loop open-circuit HST, 156
Operating torque, 127
Orbiting gerotor motor, 130
Orifice area, 57, 90
of disk valves, 303
formulas, 303
of needle valves, 303
of round holes, 303
of simple ball valves, 303
of simple spool valves, 303
Orifice coefficient, 58, 257
Orifice equation, 10–11, 58, 300
O-ring seals, 219–220
O-ring type fittings, 97
Oscillating motors. See also Motor(s)
defined, 111, 126
operating parameters, 139–140
Oscillating rotary actuators, 138–140
Outlet filters, 205–206
Outlet line strainer, 205–206
Output reaction, 261
Outside diameter, 93, 96
Overall efficiency, 112, 129
Overall pump efficiency, 43
Overdamped system, 280
Overlapped valves, 61, 89
Overshoot, 279–280
Oxidation stability, 199
P
Partial priority, 76
Pascal, Blaise, 6
Pascal’s law of pressure, 6–8, 299
Petroleum-based fluids, 100, 200320 Index
Phosphate esters, 201
Pilot-operated check valves, 72
Pilot-operated solenoid valves, 83
Pilot relief, 65–66
Pin-lock couplings, 95
Pintle-type radial pump, 40–41
Piston, 113
actuating, 186
boosting, 186
Piston pumps, 34–41. See also Pump(s)
axial, 34, 35
inline, 34, 35
radial-type, 40
Piston shoes, 34
Piston-type hydraulic motors, 133–135
axial, 134–135
radial, 133–134
Pivot joints, 123
Pneumatic power systems, 2
Polyglycols, 200–201
Polytetrafluorethylene (PTFE), 93–94
Poppet valve, 55, 56
Position controls, 289
Positions, 73
Positive displacement pumping, 25, 26–27, 26
Potential energy, 253
Power
absorption, 167
conversion factors, 305
defined, 8
efficiency, 43
mechanical, 14
Power-absorbing devices, 170–175
hydraulic fluid springs, 173–175
hydraulic shock absorbers, 170–173
Power deployment components, 17–18, 17
Power deployment subsystem, 2–3
Power distribution
components, ISO/ANSI standard
symbols for, 17
defined, 2
energy losses in, 103–105
heat generation in, 103–105
Powered lands, 61
Power generation subsystem, 2
Power-matching control, 47
Power regeneration, 167, 185–191
external power regenerators, 185
functions of, 185
hydraulic braking chargers, 189–190
hydraulic power intensifiers, 186–188
internal power regenerators, 185
two-speed hydraulic cylinders, 188–189
Power regulation subsystem, 3
Power storage, 167
components, 18, 18
devices, 176–185
Power-to-weight ratio, 4
Power transmission
electrical, 1–2
fluid, 2
hydraulic cylinder, 121–123
hydraulic fluids and, 195
of hydraulic motors, 140–145
in machinery systems, 1–2
mechanical, 1
P-port, 73
Pressure, 6
booster, 186
defined, 306
drop, 90
intensifier, 119, 169
override, 64
overshoot, 40
Pressure-compounded flow control
valves, 78–79
Pressure control circuits, 223–227. See also
Hydraulic circuits
balancing circuits, 226
bleed-recharge circuit, 226–227, 227
defined, 223
line-relief circuit, 223, 224
pressure-reducing circuit, 225–226
two-stage pressure-regulating
circuit, 224
Pressure control valves, 16, 64–71
constant-pressure-reducing control,
67–68
counterbalance valves, 69–70, 70
cracking pressure, 64
direct-acting relief valves, 64–65
fixed-pressure-reducing control, 68
full-flow pressure, 64
main relief, 65–66
pilot relief, 65–66
pressure override, 64
sequence valves, 68–69, 69
underloading valves, 70–71
Pressure limiting, 45–46
compensation, 45
defined, 42
flow-sensing control, 46
load sensing with, 47–48
Pressure-reducing circuit, 225–226
Pressure-reducing valves, 66–67
Priority control, 76Index 321
Programmable electrohydraulic circuits,
247–249
Programmable electrohydraulic valves, 87–88, 88
Proportional control valves, 17, 81, 285–286
Proportional directional control valves, 85–86
Proportional-integral-derivative (PID) control,
292–293
Proportional solenoid drivers, 81
Pulsation absorber, 176
Pulse width, 83
Pulse-width modulation (PWM), 82–83, 83
Pump-controlled motors, 240
Pump efficiency, 14
Pump inlet lines, 99
Pump port, 56
Pump(s), 25–41
fixed-displacement, 16, 33, 241
gear, 27–32
maximum speed, 25
minimum speed, 25
overview, 25–26
piston, 34–41
positive displacement pumping, 26–27, 26
rated speed, 25
speed, 299–300
vane, 32–34
variable-displacement, 16, 241–242
Pump slippage, 30
Pump-to-work path, 56
Pump-unloading circuits, 235–236, 235
Q
Quick-disconnect coupling, 95
R
Radial-piston motors, 133–134. See also Motor(s)
cam-type, 135
static balanced, 136–137, 137
Radial-type piston pump, 40
Ram cylinders, 116–117, 117
Rated discharge pressure, 25
Rate flow, 63
Reciprocating-type pump, 27
Recycled fluid, 115
Reference point, 281
Reinforcement layer, 93
Relative density, 197
Relief valve, 204
Replenishing and cooling circuits, 239
Resistance-overcoming torques, 127
Response delay, 62, 291
Response time, 280
Retracting ring, 34
Retraction cycle, 114
Return lands, 61
Return lines, 99
Ring-lock, 96
Rise time, 279–280
Rod, 113
Rod end, 109
Roller-lock couplings, 95
Rolling-vane motors, 135, 136. See also Motor(s)
Rotary abutment motors, 139
Rotary actuators
defined, 109
oscillating, 138–140
Rotary bladder motors, 139
Rotary cylinders, 126
Rotary-type pumps, 27
Round holes, orifice area of, 303
Running torque, 127
Rust prevention, 199
S
Saturated pressure drop, 213
Saturation, 270
Saturation level, 209
Saturation zones, 62
Screw pumps, 31–32
Seals, 113, 218–220. See also Hydraulic cylinders
cross-section of, 220
O-ring, 219–220
U-shaped lip seal, 220
V-shaped lip seal, 220
Y-shaped lip seal, 220, 221
Second-order differential equation, 255
Sequence valves, 68–69, 69
Sequencing control circuits, 233–234
Servo, 86
Servo control valves, 285–286
Servo drivers, 81
Settling time, 279
Shock absorbers, 170–173
annular clearance type, 170
configurations of, 170, 171
defined, 167, 169
multiple-orifice type, 170
operations, 175
orivis type clearance type, 170
simple orifice type, 170
spear-type, 170
stepped spear type, 170
tapered spear type, 170322 Index
Shock damper, 177
Shuttle check valves, 72
Shuttle valves, 72
Single-acting cylinders, 116
Single-acting intensifiers, 187
Single-phase manifolds, 91–92
Single-rod double-action cylinder, 109, 113
Single-vane actuators, 138–139
SI unit system, 18
Society of Automobile Engineers
(SAE), 210
Soft-shifting, 57
Solenoid control valves, 286
Solenoid drivers, 81–83
Solid particle contamination, 208–209
Solutions to selected exercise problems,
307–310
Specific gravity, 197
Speed booster, 188, 190–191
Speed control
dial adjustment approach, 143
of hydraulic motors, 140–145
Speed control circuits, 228–233. See also
Hydraulic circuits
bleed-off circuits, 229
closed-center, 231
meter-in circuits, 229
meter-out circuits, 229
open-center, 230
secondary adjustment, 233
speed-increase circuits, 231–232
speed-reducing circuits, 232–233
Speed-increase circuits, 231–232
Speed-reducing circuits, 232–233
Speed response transfer function, 268
Spool shoulders, 57
Spool strokes, 62, 291
Spool valves. See also Valve(s)
defined, 56
efficiency, 260–261
flow velocity angle, 60
operating principle of, 57
orifice area of, 303
overlapped, 61
power output, 260–261
spring constant, 60
underlapped, 60
valve flap, 60, 61
valve-transform curve, 62
Spring, 253
compression or stretching of, 253
stiffness of, 253
Spring constant, 60
Spring-loaded accumulators, 178–179
Spring-return single-acting
cylinders, 116
Stall torque, 144
Stall torque efficiency, 112, 155
STAMPED procedure, 98, 101
Standard unit system, 18
Standby pressure, 47
Starting torque, 127
Static balanced radial-piston motors,
136–137, 137
Static resistance, 127
Steady-state error, 279–281
Stiffness
hydraulic, 266–267
of spring, 253
Stimuli input, 261
Straight runs, 96
Strainers, 211–212
Suction chambers, 27
Suction lines, 99
Summing junction, 261
Summing points, 268
Surface foam, 199
Swash plate, 34
Switch-mode power supplies, 83
Swivel fitting, 103
Swivel joint, 103
Synchronizing control circuits, 234
Synthetic esters, 200
Synthetic hydrocarbons, 201
Synthetic solutions, 202
System analysis, 261–272
closed-loop, 284–285
system block diagram, 261–266
system performance characteristics,
270–272
system state-space equations,
268–269
transfer function, 261–266
transfer function simplification,
266–268
System block diagram, 261–266
of basic feedback control system, 281
of basic modulated feedforward control
systems, 291
System load, 272
System performance characteristics,
270–272
System schematics, 4–5, 5
System state-space equations, 268–269Index 323
T
Takeoff point, 261
Tandem-center valve, 75, 87
Tandem state, 119
Tank port, 56
Telescopic cylinders, 117–118, 117
Theoretical output speed, 128
Theoretical output torque, 127
Thermal stability, 199
Three-way position valve, 73
Throttling control, 57
Torque
conversion factors, 306
defined, 6
efficiency, 44
motor, 86
ripple, 128
stall, 144
starting, 127
theoretical output, 127
torque-limiting compensator, 48–50
torque-to-speed ratio, 151
total, 127
Total pressure-flow coefficient, 267
Total torque, 127
T-port, 73–74
Transfer function, 261–266
of major blocks, 268
simplification, 266–268
of summing points, 268
Transient operating state, 121
Transient response, 279–281
Two-speed hydraulic cylinders, 188–189
defined, 169
flow regeneration mode, 188–189
heavy-load and low-speed
mode, 188
light-load and high-speed mode, 188
normal mode, 188
Two-stage pressure-regulating
circuit, 224
U
Unbalanced vane pumps, 32
Undercondition valve control, 72
Underdamped system, 280
Underlapped spool valves, 60
Underloading valves, 70–71
Unit box, 261
U-shaped lip seal, 220
V
Valve-controlled systems,
257–261
hydraulic damping ratio, 268
load area, 258
load flow rate, 258
load pressure, 258
Valve control of motor motion
(VCMM), 141–142
Valve-opening areas, 85
Valve(s)
control. see Control valves
flap, 60, 60
land, 61
plate, 34, 131
ports, 73
spool. see Spool valves
transform curve, 291
underloading, 70–71
Valve-transform curve, 62
Vane actuators, 138
Vane motors, 131–132, 131
Vane pumps, 32–34. See also Pump(s)
balanced, 32, 33
cam ring, 32
housing, 32
unbalanced, 32, 32
Vapor bubbles, 209
Variable-displacement axial-piston
motors, 135
Variable-displacement
motors, 241–242
Variable-displacement pumps,
16, 241–242
Variable-power transmissions, 146
Variable pump-fixed motor HST,
148–149, 241
Variable pump-variable motor HST,
149–151, 242
Variable-torque transmissions, 146
Vegetable oils, 201
Velocity
controls, 287–288
conversion factors, 306
Vibration, 253–254
Viscosity index, 197
Volume, conversion factors, 305
Volumetric efficiency, 43,
112, 128
Volumetric flow rate, 77
V-shaped lip seal, 220324 Index
W
Water-based fluids, 201–202, 202
Water contamination, 209
Water glycol, 201
Ways, 73
Weight flow rate, 77
Weight-loaded hydraulic accumulator, 178
Wet-armature solenoid, 82
Winter number, 198
Wire-reinforced hoses, 93
Work, 8
Working lines, 16
Work ports, 56
Work-to-tank path, 56
Y
Y-shaped lip seal, 220, 221
Z
Zero gain, 90
Zinc dithiophosphate, 199

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