Hydraulic transmission technology

Author: Chief Editor: Li Peilu
Publisher:
Publish Date: 2004-11-01
Features: This book elaborates on the fundamental theories of hydraulic transmission, systematically introduces the components of hydraulic transmission, and organically combines them with basic circuits, highlighting the analysis of typical systems. It teaches the design methods of hydraulic systems and also covers the application of modern proportional control, servo control, and new technologies. The book also provides a brief introduction to the use, maintenance, and fault analysis of hydraulic systems. It serves as a reference for engineering technicians engaged in research and design of hydraulic transmission, as well as a teaching material for specialized courses in higher technical colleges. Excerpt:
(4) Auxiliary components, such as the hoses, oil tanks, and filters shown in Figure 12. Auxiliary components are essential elements of a hydraulic system, playing a crucial role in ensuring its reliable operation.
(5) Working medium, i.e., hydraulic oil. Most machine tool hydraulic systems use mineral oil as the working medium.
Section II: Graphic Symbols for Hydraulic System Diagrams
In Figure 1-2, the components of the hydraulic system are illustrated using semi-structural diagrams. This type of diagram is highly intuitive and easy to understand but difficult to draw, especially when the system contains a large number of components. In practical engineering applications, simple graphic symbols are generally used to draw hydraulic system diagrams, except in certain special cases. For the hydraulic system shown in Figure 1-2, if it is drawn using the hydraulic graphic symbols specified by the national standard GB786-76, the system diagram is as shown in Figure 1-3. The symbols in the diagram represent only the functions and connection paths of the components, not their specific structures or parameters, nor the exact positions of system pipelines or component installations. The meaning of the numbering in the diagram is the same as that in Figure 1-2. Common hydraulic system diagram graphic symbols are listed in the appendix of this book.
Section III: Advantages and Disadvantages of Hydraulic Transmission
Compared to mechanical and electrical transmission, hydraulic transmission has the following advantages:
(1) It can achieve smooth, stepless speed regulation within a wide range, with a speed regulation ratio generally ranging from 100:1 to 2000:1.
(2) Under the same power conditions, the volume and weight of the energy conversion components in hydraulic transmission are smaller.
(3) It operates smoothly with low reversing impact, making it easy to achieve frequent direction changes.
(4) It facilitates overload protection, and the working oil enables self-lubrication of transmission parts, resulting in a longer service life.
(5) It is simple to operate and easy to automate, especially when combined with electrical control, making it convenient to implement complex automatic working cycles.
(6) Hydraulic components are easily standardized, serialized, and generalized, facilitating design, manufacturing, and widespread use.
The main disadvantages of hydraulic transmission are:
(1) Leakage in hydraulic transmission and the compressibility of the fluid make it impossible to guarantee a strict transmission ratio.
(2) Hydraulic transmission suffers from significant energy losses (leakage loss, friction loss), resulting in low transmission efficiency and making it unsuitable for long-distance transmission.
(3) Hydraulic transmission is sensitive to temperature variations, making it unsuitable for operation under very high or very low temperatures.
(4) It can be difficult to identify the causes of faults in hydraulic transmission.
Overall, hydraulic transmission has many advantages. With the continuous advancement of science and technology, some of its disadvantages will gradually be overcome.