Hydraulic and Pneumatic

Transmission

First, let me introduce myself.I was a student thirty years ago. I attended Tongji university in 1977, graduated in 1981. After that, I became an engineer, working at electrical machine design in Zhengzhou mechanical institute of pre pre ministry of water resources and electricity. In 1985 I became a teacher of mechanical engineering department, North China institute of water conservancy and hydroelectric power. My main lectures include Hydraulic and Pneumatic Transmission, Hydrodynamic power Transmission, Hydraulic Servo System, computer program design, AutoCAD and so on, particully, I have 20-year experince of Auto CAD utilization and development.

Now I’m a professor and master supervisor. My interests include fluid power, new product development. I have presided over five scientific and technical projects and joined many other projects. I have designed a series of hydraulic power station hoists. As a specialist, I frequently attends various design appraisal conferences. I’m the author of over 20 papers. Cooperating with others I have published two books. In academy, I have made great progress. I created a new coordinate system—generalized torus coordinate system. I established a differential equation. More importantly, my research results refresh the history of hydodynamic torque converter design and deepen people’s design phylosophy.

Second, let me introduce the course. Hydraulic and pneumatic transmission is modern industry technology(as advanced military technology during the world war), which is called the blood of modern industry. Most sophisticated mechanical movments is accomplished with the help of fluid power. The course includes fluid mechanics, hydraulic elements, hydraulic system and pneumatic transmission. On the other hand, the course deals with mechanism, structure and control. Particularly, the hydraulic control is the pyramid top of mechnical discipline.

It should be noted that it is difficut to study the course. mystery→understanding→feeling comfortable→gain insight Bilingual teaching Step by step, gradually, more and more After completing the course, you can make great progress in both knowledge and English if you study hard.

Third, something is of particular importance to you. If you are interested in master degree, welcome to become my post graduates. Furthemore, if you are interested in doctor degree, the course will lay a solid foundation for your progress.

Keep in mind that “Learning is a journey of discovery that never ends”.

Remember that methematics, English and are three fundamental stones that surport your knowledge. Mathematics is the queen of scince.—Gauss Your future research results will depends on your mathematic application. Foreign language ia weapon of life—Marx Englis is the vector of important information(80%). Computer application is a main approch of scientific research and engineering application.

Objectives: The purpose of this chapter is to describe: 1. Operation of hydraulic systems. 2. Power elements, actuators, control components and Ancillary components . 3. fluid power diagram and symbols Upon completing this chapter, you should be able to: 1. Explain the operation of the various types of elements. 2. Identify the graphical symbols used for elements. 3. Understand the advantages and disadvantages of fluid power.

Chapter 1 Introduction to fluid powerChapter 1 Introduction to fluid power

1.1 Transmission and transmission classification1.1 Transmission and transmission classification

A whole machine consists of a prime mover, a transmission section, a control section and an end-use device(working machine).

The commonly used prime movers are electric motors, gasoline engines and diesel engines.

According to working media, the transmission mechanism can be classified as mechanical transmission, electric transmission and fluid transmission.

1.1.1 Transmission1.1.1 Transmission

1.1.2 classification1.1.2 classification

Fluid power is that energy transmitted and controlled by means of a pressurized fluid, either liquid or gas.

1.1.3 FLUID POWER DEFINITION

The fluid transmission can be classified as hydrostatics transmission, hydrodynamics transmission, pneumatics transmission and viscosity transmission.1 Several words:

2 History of fluid power

Fluid power Hydraulic transmission Hydrostatic transmissionHydrodynamic transmission

In the seventeen century, Pascal put forward the principle of fluid power In the eighteen century, the first press was manufactured

1.1 Transmission and transmission classification1.1 Transmission and transmission classification

Before electrical power was developed , fluid power had being used to drive hydraulic equipment such as cranes, presses, winches, extruding machines, hydraulic jacks, shearing machines, and riveting machines.

The modern era of fluid power is considered to have begun in 1906 when a hydraulic system was used for elevating and controlling guns on the battleship USS Virginia. During and after World War II the aviation and aerospace industry provided the impetus for many advances in fluid power technology .

Today fluid power is used extensively in practically every branch of industry.

1.1 Transmission and transmission classification1.1 Transmission and transmission classification

1.2 Theory of hydraulics and hydraulic system

1.2.1 Theory of hydraulics Figure1.1 Principle of operation of grinding machine’s hydraulic system1-tank; 2-filter; 3,12,14-return line; 4-pump; 5-spring; 6-steel ball;7-relief valve; 8,10-pressure line; 9-manually actuated directional control valve ; 11,16-hand lever;13-throttle valve;15-directional valve; 17-piston; 18-cylinder;19-work table.

(a) 1→2→4→9→13→15 → 18(left) 18(right)→15→1 The work table moves to right.

(b)1→2→4→9→13→15 → 18(right) 18(left)→15→1 The work table moves to left.

(c)1→2→4→9→1 The work table stops. The pump unloads

Valve 13—throttle valve, which is used for speed

control.

Valve 5—relief valve, which is used to maintai

n the system pressure constant.

1.2. 2 COMPONENTS OF HYDRAULIC SYSTEM

(1) A power component(pump) which forces the liquid through the system, and converts mechanical power to fluid power.

(2)Actuators (Cylinders or motors) which convert fluid power to linear or rotary mechanical power.

(3)Control components : including valves, which control the direction, pressure and rate of flow. Directional valve 15 is a control component.

(4)Ancillary hydraulic components: Filters, regulators, pipes, reservoirs, etc.

1.2 Theory of hydraulics and hydraulic system

1.2.3 fluid power diagram and symbols

relieve valve

cylinder

pump

motor

check valve

1.2 Theory of hydraulics and hydraulic system

1.3 Advantage and disadvantage of fluid power

1.3.1 The advantages of fluid power

(1) High horsepower, low weight ratio. Hydraulic components are compact and lightweight .

(2)Easy, accurate controlling ,reversible, infinitely variable speed and load control completely automatic operations.

(3)Accurate position control for linear and rotary elements, and variable speed control. (4)Power linkage where kinematic linkage is impractical, convenient method of power transmission over long distance.

(5)Reduction of wear by the self-lubrication action of the transmission medium.

(6) simplicity, safety, great flexibility, reliability and economy. (7) Standardization. The fluid power industry has established design and performance standards for hydraulic and pneumatic products.

1.3.2 Some of the major disadvantages of hydraulic systems

(1) Impairment of system operation by contamination (2) Hydraulic fluid leakage (3) Fire hazards with flammable hydraulic fluids (4) Hydraulic lines can burst, possibly resulting in injuries to people due to high-speed oil jets and flying pieces of metal, if proper design is not implemented. (5) Adequate oil filtration must be maintained

1.3 Advantage and disadvantage of fluid power