Hydropneumatic Suspension Systems

Description

Hydropneumatic suspension systems combine the excellent properties of gas springs with the favourable damping properties of hydraulic fluids. The advantages of these systems are particularly appropriate for mobile applications, such as agricultural and construction equipment as well as passenger cars, trucks and busses. Based on his 20 years of experience with this technology, Dr. Bauer provides in this book an extensive overview of hydropneumatic suspension systems. Starting with a comparison of different types of suspension systems, the author subsequently describes the theoretical background associated with spring and damping characteristics of hydropneumatic systems. Furthermore, he explains the design of the most important system components and gives an overview of level control systems, various special functions, patents and design examples. Finally, an outlook for future hydropneumatic suspension systems is discussed. Compared to the first edition, this new edition puts an additional focus on damping functions as well as applications / projects and contains various additional details such as proportional valves, all-wheel suspension or dediated power supply. Furthermore, suspension testing has been added as a new chapter. Preface Contents 1 Suspension Systems Basics 1.1 Requirements for Suspension Systems 1.1.1 Minimize Accelerations on the Isolated Side 1.1.2 Equalize Variations of Vertical Wheel Forces 1.2 Suspension Technology Basics 1.2.1 General Setup of a Suspension System 1.2.2 General Behavior of a Suspension System 1.2.3 Alteration of Suspension Parameters 1.3 Hydropneumatic Suspension Compared to Other Suspension Methods 1.3.1 Comparison of Spring Characteristics 1.3.2 Comparison of Damping Characteristics 1.3.3 Level Control 1.3.4 Non-functional Requirements 1.4 Applications for Hydropneumatic Suspension Systems 2 Spring and Damping Characteristics of Hydropneumatic Suspension Systems 2.1 General Setup and Working Principle 2.2 Spring Characteristics 2.2.1 Thermodynamic Background 2.2.2 Calculation Predeterminations 2.2.3 Non Preloaded Hydropneumatic Suspension Systems 2.2.4 Systems with Mechanical Preload 2.2.5 Systems with Constant Hydraulic Preload 2.2.6 Systems with Variable Hydraulic Preload 2.3 Damping Characteristics 2.3.1 Boundary Friction Damping 2.3.2 Fluid Friction Damping 2.3.3 End-of-Stroke Damping 2.4 Combined Operation of Spring and Damper 3 Dimensioning of the Hydropneumatic Suspension Hardware 3.1 Dimensioning of the Hydraulic Spring Components 3.1.1 Cylinder 3.1.2 Accumulator Gas Precharge 3.1.3 Detailed Calculation of p0 and V0 3.2 Dimensioning of the Hydraulic Damping Elements 3.2.1 Single-Acting Cylinder in a System Without Hydraulic Preload 3.2.2 Double-Acting Cylinder in a System Without Hydraulic Preload 3.2.3 Double-Acting Cylinder in a System with Hydraulic Preload 3.2.4 End-of-Stroke Damping 4 Hydraulic Components Design 4.1 Cylinders 4.1.1 Function and Requirements 4.1.2 Types of Cylinders 4.1.3 Sealing Elements 4.1.4 End-of-Stroke Damping 4.1.5 Types of Support Elements 4.2 Accumulators 4.2.1 Function and Requirements 4.2.2 Types of Accumulators 4.2.3 Methods to Reduce Diffusion Pressure Loss 4.2.4 Usage of Pressure Relief Valves 4.2.5 Integration into Available Design Space 4.3 Flow Resistors 4.3.1 Non Adjustable Orifices and Throttles 4.3.2 Flow Direction Depending Resistors 4.3.3 Adjustable Flow Resistors 4.4 Hydraulic Lines and Fittings 4.4.1 Function and Requirements 4.4.2 Required Flow Cross Section 4.4.3 Tubes 4.4.4 Hoses 4.4.5 Fittings 4.5 Control Manifolds 4.5.1 Functions and Requirements 4.5.2 Block Design 5 Level Control 5.1 Self-Pumping Suspension Elements 5.2 Mechanical Level Control with External Hydraulic Power Supply 5.3 Electronic Level Control with External Hydraulic Power Supply 5.3.1 Function 5.3.2 Hydraulic Circuits Using On/Off-Valves 5.3.3 Hydraulic Circuits Using Proportional Valves 5.3.4 Control Algorithms 5.4 Electronic Level Control with Dedicated Power Supply 6 Special Functions of Hydropneumatic Suspension Systems 6.1 Suspension Lockout 6.1.1 Lockout by Blocking the Hydraulic Circuit 6.1.2 Lockout at the Compression End Stop 6.1.3 “Quasi-lockout” Through High Spring Stiffness 6.2 Adjustment of the Zero Position 6.3 Alteration of Roll and Pitch Behavior 6.3.1 Coupling Cylinders on Corresponding Sides 6.3.2 Decoupling Cylinders 6.3.3 Coupling Double-Action Cylinders on Opposite Sides 6.4 Spring Rate Adjustment by Selective Connection of Accumulators 6.5 Tire-to-Ground Force Optimization in All-Wheel Suspension Systems 7 Suspension Testing 7.1 Goals of Suspension Testing 7.1.1 Functional Testing 7.1.2 Durability Testing 7.2 Test Scenarios and Methods 7.3 Measurements, Evaluation and Optimization 7.3.1 Pressure 7.3.2 Position/Displacement 7.3.3 Acceleration 7.3.4 Online Versus Offline Evaluation 7.4 Typical Project Testing Steps 7.4.1 Initial Function Testing/Analysis 7.4.2 Hardware-In-The-Loop (HIL) Testing 7.4.3 Laboratory Functional Testing 7.4.4 Machine Functional Testing 7.4.5 Durability Testing 8 Design Examples 8.1 Tractor Front Axle Suspension TLS by John Deere 8.2 Passenger Car Axle Suspension by Citroen 8.3 Suspension Projects—Lessons Learned 9 Important Patents 9.1 Improvement of Suspension Characteristics 9.1.1 DE1755095 9.1.2 DE19719076 9.1.3 DE10107631 9.1.4 DE10337600 9.1.5 DE4221126 9.1.6 DE4234217 9.1.7 US9039021 9.1.8 DE4223783 9.1.9 US6167701 9.1.10 DE19949152 9.1.11 US6398227 9.1.12 DE102008012704 9.2 Roll Stabilization and Slope Compensation 9.2.1 GB890089 9.2.2 DE3427508 9.2.3 DE10112082 9.2.4 US4411447 9.2.5 US6923453 9.3 Suspension Lockout 9.3.1 US3953040 9.3.2 DE4308460 9.3.3 DE4032893 10 Looking into the Future 10.1 Components 10.2 Systems 10.3 Energy Consumption 10.4 Trend Towards Electronics Index of Symbols and Abbreviations Dimensions and Dimension Related Parameters Forces and Force Related Parameters Accumulator Related Parameters and Pressures Parameters Defining the Dynamic Suspension Behavior Miscellaneous Parameters General Use of Indices References Index