SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING UNIT SEVEN HYDRAULIC TRANSMISSION hydraulic液力的 LESSON ONE INTRODUCTION transmission传动 For many years a hydraulic system was plumbing considered the result of plumbing together a 管件总称 number of components. Also, a hydrauliccomponent system has been considered merely the source组成部分 of power for control servos. Each of these servo faHE concepts can lead to basic errors. Following伺服系统 either of these guide lines can result in inadequate systems, which are inadequate, unstable, or a 不充足的 combination of the two unstable不稳定的
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING UNIT SEVEN HYDRAULIC TRANSMISSION LESSON ONE INTRODUCTION For many years a hydraulic system was considered the result of plumbing together a number of components. Also, a hydraulic system has been considered merely the source of power for control servos. Each of these concepts can lead to basic errors. Following either of these guide lines can result in systems, which are inadequate, unstable, or a combination of the two. hydraulic 液力的 transmission 传动 plumbing 管件总称 component 组成部分 servo 伺服 伺服系统 inadequate 不充足的 unstable 不稳定的
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING From an operational standpoint, any hydraulic system can be divided into four accumulator 蓄能器 logical segments: The power input segment, the tube connector power transmission system, the control devices管接头 and the power output portion. The power input swivel joint gment usuall! consists of pumps and转节,旋转接头 accumulators. The power transmission system flexible hose th includes tubing, tubing connectors, swivel joints and flexible hose. Flow control valves, relief valve 溢流阀 pressure control val ves. And relief valves make oscillatory up the control elements. The power output摆动的,振荡的 portion usually consists of rotary and actuator oscillatory motor or linear actuators. Because al most all practical hydraulic systems can be 执行机构 divided into these same four basic segments they will be considered in detail later
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING From an operational standpoint, any hydraulic system can be divided into four logical segments: The power input segment, the power transmission system, the control devices and the power output portion. The power input segment usually consists of pumps and accumulators. The power transmission system includes tubing, tubing connectors, swivel joints and flexible hose. Flow control valves, pressure control valves. And relief valves make up the control elements. The power output portion usually consists of rotary and oscillatory motor or linear actuators. Because almost all practical hydraulic systems can be divided into these same four basic segments, they will be considered in detail later. accumulator 蓄能器 tube connector 管接头 swivel joint 转节，旋转接头 flexible hose 软管 relief valve 溢流阀 oscillatory 摆动的，振荡的 actuator 执行机构
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Paralleling the improvement in hydraulic fluids and other materials has been an increase in the complexity and sophistication sophistication of hydraulic systems. Most early hydraulic改进,复杂化 systems were no more complex than the pump 泵 system in an automobile hydraulic jack. The Jack contains a hand operated pump which draw(a) draws oil from a reservoir. Oil is pumped past reservoir iH fA a check or non-return valve into a linear check valve单向阀 actuator. The oil flowing into the actuator piston活塞 forces the piston to move. The moving piston can do work on an outside load. a valve controls flow from the piston back to the reservoir
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Paralleling the improvement in hydraulic fluids and other materials has been an increase in the complexity and sophistication of hydraulic systems. Most early hydraulic systems were no more complex than the system in an automobile hydraulic jack. The jack contains a hand operated pump which draws oil from a reservoir. Oil is pumped past a check or non-return valve into a linear actuator. The oil flowing into the actuator forces the piston to move. The moving piston can do work on an outside load. A valve controls flow from the piston back to the reservoir. sophistication 改进，复杂化 pump 泵 draw 吸（入） reservoir 油箱 check valve 单向阀 piston 活塞
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Through the use of power driven pumps and directional control valves these simple systems have grown so that a sequentially number of loads can be handled相继的,结果的 independently or sequentially from the sameamplifier放大器 power source. Power hydraulics is a power amplifier in which a small effort applied to boost促进 a control device results in a large amount of refinement work performed on a load. With boost I精确,精心安装 servos, hydraulic power aids the operator's irreversible effort. Further refinement has led to the不可逆的 irreversible servo-mechanism in which the operators effort is separated from the load by the rigidity of the oil in the actuating cylinder or motor
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Through the use of power driven pumps and directional control valves these simple systems have grown so that a number of loads can be handled independently or sequentially from the same power source. Power hydraulics is a power amplifier in which a small effort applied to a control device results in a large amount of work performed on a load. With boost servos, hydraulic power aids the operator’s effort. Further refinement has led to the irreversible servo-mechanism in which the operator’s effort is separated from the load by the rigidity of the oil in the actuating cylinder or motor. sequentially 相继的，结果的 amplifier 放大器 boost 促进 refinement 精确，精心安装 irreversible 不可逆的
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING ADVANTAGES OF HYDRAULIC SYSTEMS What are the reasons for using hydraulic power in heavy-duty industrial, mobile and aircraft designs? Even though pneumatic control systems preceded hydraulic servos, and electrical power is in more widespread use than hydraulic, systems which require high power amplification or which must pack great energy into a small space are almost invariably hydraulic If hydraulic power transmission and amplification were to be compared with pneumatic, electrical and mechanical systems. these are some of the reasons for specifying hydraulic power mplification放大,加强 invariably不变的
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING ADVANTAGES OF HYDRAULIC SYSTEMS What are the reasons for using hydraulic power in heavy-duty industrial, mobile and aircraft designs? Even though pneumatic control systems preceded hydraulic servos, and electrical power is in more widespread use than hydraulic, systems which require high power amplification or which must pack great energy into a small space are almost invariably hydraulic. If hydraulic power transmission and amplification were to be compared with pneumatic, electrical and mechanical systems, these are some of the reasons for specifying hydraulic power. amplification 放大，加强 invariably 不变的
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING 惯性消 t Hydraulic motors possess an extremely high ratio of torque to inertia. Because of this, very little of the available torque is dissipated in accelerating the motor, most of the torque can be 除 applied directly to the load. Acceleration rates for unloaded hydraulic motors. for example, vary from about 0.3x105radians per second squared for larger sizes at 3000psi to 3. 4x10radians per second squared for smaller motors. No other transmission system produces motors having acceleration rates anywhere near these values. Higher supply pressures develop accordingly higher acceleration rates 加速度 Hydraulic motors develop no counter electro-motive force as do electrical motors There fore. the acceleration rate is essentially constant over their design speed ranges psi= pound per square inches每平方英寸磅
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Hydraulic motors possess an extremely high ratio of torque to inertia. Because of this, very little of the available torque is dissipated in accelerating the motor; most of the torque can be applied directly to the load. Acceleration rates for unloaded hydraulic motors, for example, vary from about 0.3105 radians per second squared for larger sizes at 3000psi to 3.4105 radians per second squared for smaller motors. No other transmission system produces motors having acceleration rates anywhere near these values. Higher supply pressures develop accordingly higher acceleration rates. Hydraulic motors develop no counter electro-motive force as do electrical motors. Therefore, the acceleration rate is essentially constant over their design speed ranges. 惯 性 消 除 加速度 psi=pound per square inches 每平方英寸磅
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Hydraulic devices can generate much more power in the same volume than can electrical devices The reason for this lies in the characteristics of the materials used in electrical equipment. The very best armature steels can develop only the equivalent of bout 200 psi in tractive power before they become saturated. By comparison, 3000 psi hydraulic equipment is very common and pressures up to 5000 psi are not rare 使饱和 电枢,转子 Because of the greater pressure density, hydraulic equipment in power sizes greater than I hp. tends to be mach smaller than electrical motors and somewhat smaller than pneumatic motors horsepower Hydraulic motors support heavy or springy loads much better than do electrical or pneumatic motors. Looking from the load back into the motors, electrical fields or compressed gasses are quite soft. The relatively incompressible oil is however. stiff
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Hydraulic devices can generate much more power in the same volume than can electrical devices. The reason for this lies in the characteristics of the materials used in electrical equipment. The very best armature steels can develop only the equivalent of bout 200 psi in tractive power before they become saturated. By comparison, 3000 psi hydraulic equipment is very common and pressures up to 5000 psi are not rare. Because of the greater pressure density, hydraulic equipment in power sizes greater than l hp. tends to be mach smaller than electrical motors and somewhat smaller than pneumatic motors. Hydraulic motors support heavy or springy loads much better than do electrical or pneumatic motors. Looking from the load back into the motors, electrical fields or compressed gasses are quite soft. The relatively incompressible oil is, however, stiff. 使饱和 电枢，转子 horsepower
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Hydraulic transmission systems efficiently transmit power farther than do mechanical systems, but not as far as electrical systems Hydraulic transmission systems may be less hazardous than electrical systems and are far safer than mechanical power transmission systems 危险的 Hydraulic oil is a good heat conductor so that the heavily loaded working area stays relatively cool. Heat generated at the working interface is conducted away rapidly. The working areas can therefore be made small because heat absorbing mass is not needed. Because of this and because of the high-pressure density, hydraulic motors weigh less than one pound per horsepower. Horsepower to weight ratios of up to 2.5 are not uncommon
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Hydraulic transmission systems efficiently transmit power farther than do mechanical systems, but not as far as electrical systems. Hydraulic transmission systems may be less hazardous than electrical systems and are far safer than mechanical power transmission systems. Hydraulic oil is a good heat conductor so that the heavily loaded working area stays relatively cool. Heat generated at the working interface is conducted away rapidly. The working areas can therefore be made small because heat absorbing mass is not needed. Because of this and because of the high-pressure density, hydraulic motors weigh less than one pound per horsepower. Horsepower to weight ratios of up to 2.5 are not uncommon. 危险的
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING Hydraulic power systems al so have some drawbacks. Hydraulic oils are messy. Leaks drawback欠缺 are inevitable. The great lubricity of most hydraulic oils makes leaks and spillage very inevitable hazardous. Certain oils are excellent‖不可避免的 removers of paint and electrical insulation.spillage溢出 Hydraulic systems, particularly the high insulation绝缘 performance servo systems which use hydraulic power so efficiently, are extremelyvulnerable脆弱的 vulnerable to dirt and contamination. They contamination must constantly be watched to prevent the污染 addition or generation of contamination and hydraulic systems need expensive filtration filtration it rne to keep them clean
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING Hydraulic power systems also have some drawbacks. Hydraulic oils are messy. Leaks are inevitable. The great lubricity of most hydraulic oils makes leaks and spillage very hazardous. Certain oils are excellent removers of paint and electrical insulation. Hydraulic systems, particularly the high performance servo systems which use hydraulic power so efficiently, are extremely vulnerable to dirt and contamination. They must constantly be watched to prevent the addition or generation of contamination and hydraulic systems need expensive filtration to keep them clean. drawback 欠缺 inevitable 不可避免的 spillage 溢出 insulation 绝缘 vulnerable 脆弱的 contamination 污染 filtration 过滤
SCIENCE AND TECHNOLOGY ENGLIAH FOR MECHANICAL ENGINEERING w A rupture or burst of an element of a high-pressure aL hydraulic system can be very dangerous. The high velocity streams of oil, which results can damage eyes, pierce skin, and harm other equipment. The author has seen a piece of tubing three feet long and 1.5 inches in diameter thrown whirling for more than fifty feet when a rupture occurred in a 3000 psi line.难燃工作液 Unless fire-resistant fluids are used, hydraulic leaks create B very real fire hazards. Most petroleum based fluids are highly ko: flammable. High temperatures can be generated where a high try velocity stream of oil from a rupture impacts on a flat surface 冲击 Finally, hydraulic power is so compact that developing and controlling fractional horsepower is difficult unless the pressure density is reduced to levels where electrical power is extremely competitive
SCIENCE AND TECHNOLOGY ENGLISH FOR MECHANICAL ENGINEERING A rupture or burst of an element of a high-pressure hydraulic system can be very dangerous. The high velocity streams of oil, which results can damage eyes, pierce skin, and harm other equipment. The author has seen a piece of tubing three feet long and 1.5 inches in diameter thrown whirling for more than fifty feet when a rupture occurred in a 3000 psi line. Unless fire-resistant fluids are used, hydraulic leaks create very real fire hazards. Most petroleum based fluids are highly flammable. High temperatures can be generated where a high velocity stream of oil from a rupture impacts on a flat surface. Finally, hydraulic power is so compact that developing and controlling fractional horsepower is difficult unless the pressure density is reduced to levels where electrical power is extremely competitive. 破 裂 难燃工作液 易 燃 的 冲 击