HYDRAULIC SYSTEMS IN HEAVY CONSTRUCTION EQUIPMENT

Hydraulic Systems in Heavy Construction Equipment
P. Ciężkowski
J. Maciejewski
A. Zawadzki

The authors of the publication entitled „Hydraulic systems in heavy construction equipment”, want to acquaint students of mechanical faculties and operators of working and construction machinery with the fundamental knowledge of the designing of hydraulic systems, both their cylinders and control elements. The manuscript presents information on hydrokinetic and hydrostatic hydraulic systems. The work discusses the basic components of hydraulic systems used in working machinery, in particular: hydraulic pumps and motors, cylinders, valves, directional control valves, accumulators.

Chapter one of this book discusses the basic hydraulic components used in working machinery, their functions, purpose and presents basic calculations. Chapter two presents basic information on open, closed, constant output and constant power hydraulic systems. The ways of controlling the systems are discussed on the basis of hydraulic system diagrams. Chapter three presents current trends in drive systems used in working machines, i.e.: the driving mechanism, the turning mechanism, the rotation mechanism of the working attachment, and discusses the system of cooperation of the hydraulic cylinder with the working attachment working in the crank and lever system (chapter four). The manual presents a method for determining the forces and moments acting on work attachments generated by hydraulic cylinders (force) and hydraulic motors (torque). Chapter five is devoted to specialized control systems for work attachments in construction machinery. Chapter six presents basic information on maintenance and operation of hydraulic systems of working machinery, i.e.: unloading hydraulic systems, deaerating hydraulic systems, performing daily maintenance, replacing hydraulic components.

TABLE OF CONTENTS

Foreword 7
List of symbols. 8
1. Basic components of hydraulic systems 9
1.1. Introduction. 9
1.2. Hydraulic pumps and motors 15
1.2.1. Fundamentals of hydraulic pumps. 15
1.2.2. Types and designs of displacement pumps 24
1.2.3. Fundamentals of hydraulic motors 27
1.2.4. Types and designs of hydraulic motors 28
1.3. Hydraulic cylinders 30
1.3.1. Fundamentals of hydraulic cylinders. 30
1.3.2. Types and designs of hydraulic cylinders 33
1.4. Valves 36
1.5. Directional control valves 37
1.6. Joysticks, ways of controlling work attachments 40
1.7. Accumulators 42
1.7.1. Funadamentals of hydraulic accumulators 42
1.7.2. Types and designs of accumulators 44
1.8. Oil fi lters 45
1.9. Oil coolers 46
1.10. Quick release couplings 46
1.11. Hydraulic lines 47
1.12. Oil tanks 49
2. Overview of basic hydraulic drive systems 50
2.1. Introduction. 50
2.2. Hydrokinetic drive 52
2.3. Hydrostatic drive. 56
2.3.1. Wheeled undercarriage 57
2.3.2. Tracked undercarriage 60
2.3.3. Track sets 61
2.3.4. Road and railway machines 61
2.4. Control systems used in working machinery 62
2.5. Steering systems of wheeled vehicles 64
TABLE OF CONTENTS
6
2.6. Excavator body rotation mechanism. 66
2.7. Other drivetrains – hybrid systems 67
3. Design of hydrostatic systems in working machines 70
3.1. Introduction. 70
3.2. Open hydraulic circuit 75
3.3. Closed hydraulic circuit 76
3.4. Constant power syste m 77
3.5. Single pump control systems 78
4. Systems of cooperation between hydraulic cylinders and working attachments 82
4.1. General informations about kinematic systems used in construction machinery equipment.82
4.2. Elementary crank mechanism 85
4.3. Lever mechanism 93
4.3.1. Introduction 93
4.3.2. Determination of geometric relationships for the lever mechanism 94
4.3.3. Determination of angle γ as a function of cylinder length l 95
4.3.4. Determination of the bucket angular velocity ω3 as a function of the cylinder
length 96
4.3.5. Determination of forces and moments of forces in the lever mechanism 98
5. Selected control systems of working machinery attachments 100
5.1. Introduction. 100
5.2. Loader attachment control system with floating bucket function 100
5.3. Hydraulic system for fan drive with variable direction of rotation 105
5.4. Hydraulic diesel engine control (DHC) 106
5.5. Protection of the hydraulic line against pressure jumps caused by a sudden impact of
the cylinder on an obstacle 106
6. Hydrostatic system maintenance 107
6.1. Introduction. 107
6.2. Unloading of the hydrostatic system 107
6.3. Deaeration of the hydrostatic system 108
6.4. Oils used in the hydraulic systems of machines 108
6.5. Replacement of hydraulic lines. 113
6.6. Maintenance of hydraulic systems 114
6.7. Examples of defects in hydraulic pumps 116
Conclusions 118
References 119