Hydropneumatic Suspension Systems (eBook)

Preface 5
Contents 7
1 Suspension Systems Basics 10
1.1 Requirements for Suspension Systems 10
1.1.1 Minimize Accelerations on the Isolated Side 11
1.1.2 Equalize Variations of Vertical Wheel Forces 13
1.2 General Setup of a Suspension System 14
1.3 Hydropneumatic Suspensions Compared to Other Suspension Methods 16
1.3.1 Comparison of Spring Characteristics 16
1.3.2 Comparison of Damping Characteristics 20
1.3.3 Level Control 21
1.3.4 Non-functional Requirements 22
1.3.4.1 Component Costs 22
1.3.4.2 Design Space Requirement 22
1.3.4.3 Reliability, Safety, Robustness and Service Requirements 23
1.4 Applications for Hydropneumatic Suspensions 24
2 Spring and Damping Characteristics of Hydropneumatic Suspension Systems 27
2.1 General Setup and Working Principle 27
2.2 Spring Characteristics 29
2.2.1 Thermodynamic Background 29
2.2.2 Calculation Predeterminations 33
2.2.3 Non-preloaded Hydropneumatic Suspensions 33
2.2.4 Systems with Mechanical Preload 43
2.2.5 Systems with Constant Hydraulic Preload 49
2.2.6 Systems with Variable Hydraulic Preload 56
2.3 Damping Characteristics 58
2.3.1 Boundary Friction Damping 59
2.3.2 Fluid Friction Damping 63
2.3.3 End-of-Stroke Damping 70
2.4 Combined Operation of Spring and Damper 72
3 Dimensioning of the Hydropneumatic Suspension Hardware 75
3.1 Dimensioning of the Hydraulic Spring Components 75
3.1.1 Cylinder 77
3.1.2 Accumulator Gas Precharge 79
3.1.2.1 Non preloaded Systems and Systems with Mechanical Preload 79
3.1.2.2 Systems with Hydraulic Preload 80
3.1.3 Detailed Calculation of p0 and V0 81
3.1.3.1 Rodside Accumulator 84
3.1.3.2 Pistonside Accumulator 88
3.2 Dimensioning of the Hydraulic Damping Elements 93
3.2.1 Single-Acting Cylinder in a System Without Hydraulic Preload 93
3.2.2 Double-Acting Cylinder in a System Without Hydraulic Preload 96
3.2.3 Double-Acting Cylinder in a System with Hydraulic Preload 99
3.2.4 End-of-Stroke Damping 99
4 Hydraulic Components Design 103
4.1 Cylinders 103
4.1.1 Function and Requirements 103
4.1.2 Types of Cylinders 104
4.1.2.1 Functional Principle 106
4.1.2.2 Design Principle 108
4.1.3 Sealing Elements 109
4.1.3.1 Rod Seal System 112
4.1.3.2 Piston Seal 113
4.1.4 End-of-Stroke Damping 114
4.1.5 Types of Support Elements 117
4.2 Accumulators 119
4.2.1 Function and Requirements 119
4.2.2 Types of Accumulators 121
4.2.3 Methods to Reduce Diffusion Pressure Loss 124
4.2.4 Integration into Available Design Space 126
4.3 Flow Resistors 128
4.3.1 Non adjustable Orifices and Throttles 128
4.3.2 Flow Direction Depending Resistors 130
4.3.3 Adjustable Flow Resistors 134
4.3.3.1 Types of Adjustable Resistors 134
4.3.3.2 Activation of the Adjustment 136
4.4 Hydraulic Lines and Fittings 138
4.4.1 Function and Requirements 138
4.4.2 Required Flow Cross Section 140
4.4.3 Tubes 141
4.4.4 Hoses 143
4.4.5 Fittings 146
5 Level Control 149
5.1 Self-Pumping Suspension Elements 149
5.2 Mechanical Level Control with External Hydraulic Power Supply 152
5.3 Electronic Level Control with External Hydraulic Power Supply 155
5.3.1 Function 155
5.3.2 Hydraulic Circuits 156
5.3.3 Control Algorithms 158
6 Special Functions of Hydropneumatic Suspension Systems 165
6.1 Suspension Lockout 165
6.1.1 Lockout by Blocking the Hydraulic Circuit 166
6.1.2 Lockout at the Compression End Stop 168
6.1.3 ''Quasi-Lockout'' Through High Spring Stiffness 169
6.2 Adjustment of the Zero Position 170
6.3 Alteration of Roll and Pitch Behavior 171
6.3.1 Coupling Cylinders on Corresponding Sides 171
6.3.2 Decoupling Cylinders 172
6.3.3 Coupling Double-Action Cylinders on Opposite Sides 174
6.4 Spring Rate Adjustment by Selective Connection of Accumulators 177
7 Design Examples 180
7.1 Tractor Front Axle Suspension TLS by John Deere 180
7.2 Passenger Car Axle Suspension by Citroen 187
7.2.1 Citroens First Hydropneumatic Suspension 188
7.2.2 Hydractiv Suspension 190
7.2.3 Activa Suspension 195
8 Important Patents 199
8.1 Improvement of Suspension Characteristics 199
8.1.1 DE1755095 200
8.1.2 DE19719076 201
8.1.3 DE10107631 202
8.1.4 DE10337600 202
8.1.5 DE4221126 204
8.1.6 DE4234217 204
8.1.7 DE4223783 206
8.1.8 US6167701 207
8.1.9 DE19949152 207
8.1.10 US6398227 209
8.1.11 DE102008012704 209
8.2 Roll Stabilization and Slope Compensation 211
8.2.1 GB890089 211
8.2.2 DE3427508 212
8.2.3 DE10112082 213
8.2.4 US4411447 214
8.2.5 US6923453 215
8.3 Suspension Lockout 216
8.3.1 US3953040 217
8.3.2 DE4308460 217
8.3.3 DE4032893 218
9 Looking into the Future 220
Index of Symbols and Abbreviations 224
Dimensions and Dimension Related Parameters 224
Forces and Force Related Parameters 225
Accumulator Related Parameters and Pressures 225
Parameters Defining the Dynamic Suspension Behavior 226
Miscellaneous Parameters 226
General Use of Indices 226
References 227
Index 232