液壓系統(tǒng)-外文文獻

Hydraulic SystemA complete hydraulic system consists of five parts, namely, power components, the implementation of components, control components, no parts and hydraulic oil. The role of dynamic components of the original motive fluid into mechanical energy to the pressure that the hydraulic system of pumps, it is to power the entire hydraulic system. The structure of the form of hydraulic pump gears are generally pump, vane pump and piston pump. Implementation of components (such as hydraulic cylinders and hydraulic motors) which is the pressure of the liquid can be converted to mechanical energy to drive the load for a straight line reciprocating movement or rotational movement. Control components (that is, the various hydraulic valves) in the hydraulic system to control and regulate the pressure of liquid, flow rate and direction. According to the different control functions, hydraulic valves can be divided into the village of force control valve, flow control valves and directional control valve. Pressure control valves are divided into benefits flow valve (safety valve), pressure relief valve, sequence valve, pressure relays, etc.; flow control valves including throttle, adjusting the valves, flow diversion valve sets, etc.; directional control valve includes a one-way valve , one-way fluid control valve, shuttle valve, valve and so on. Under the control of different ways, can be divided into the hydraulic valve control switch valve, control valve and set the value of the ratio control valve. Auxiliary components, including fuel tanks, oil filters, tubing and pipe joints, seals, pressure gauge, oil level, such as oil dollars. Hydraulic oil in the hydraulic system is the work of the energy transfer medium, there are a variety of mineral oil, emulsion oil hydraulic molding Hop categories. Hydraulic principle It consists of two cylinders of different sizes and composition of fluid in the fluid full of water or oil. Water is called "hydraulic press" the said oil-filled "hydraulic machine." Each of the two liquid a sliding piston, if the increase in the small piston on the pressure of a certain value, according to Pascal's law, small piston to the pressure of the pressure through the liquid passed to the large piston, piston top will go a long way to go. Based cross-sectional area of the small piston is S1, plus a small piston in the downward pressure on the F1. Thus, a small piston on the liquid pressure to P = F1/SI, Can be the same size in all directions to the transmission of liquid. "By the large piston is also equivalent to the inevitable pressure P. If the large piston is the cross-sectional area S2, the pressure P on the piston in the upward pressure generated F2 = PxS2 ,Cross-sectional area is a small multiple of the piston cross-sectional area. From the type known to add in a small piston of a smaller force, the piston will be in great force, for which the hydraulic machine used to suppress plywood, oil, extract heavy objects, such as forging steel. History of the development of hydraulic And air pressure drive hydraulic fluid as the transmission is made according to the 17th century, Pascal's principle of hydrostatic pressure to drive the development of an emerging technology, the United Kingdom in 1795 Joseph (Joseph Braman ,1749-1814), in London water as a medium to form hydraulic press used in industry, the birth of the world's first hydraulic press. Media work in 1905 will be replaced by oil-water and further improved. World War I (1914-1918) after the extensive application of hydraulic transmission, especially after 1920, more rapid development. Hydraulic components in the late 19th century about the early 20th century, 20 years, only started to enter the formal phase of industrial production. 1925 Vickers (F. Vikers) the invention of the pressure balanced vane pump, hydraulic components for the modern industrial or hydraulic transmission of the gradual establishment of the foundation. The early 20th century Constantine (G Constantimsco) fluctuations of the energy carried out by passing theoretical and practical research; in 1910 on the hydraulic transmission (hydraulic coupling, hydraulic torque converter, etc.) contributions, so that these two areas of development. The Second World War (1941-1945) period, in the United States 30% of machine tool applications in the hydraulic transmission. It should be noted that the development of hydraulic transmission in Japan than Europe and the United States and other countries for nearly 20 years later. Before and after in 1955, the rapid development of Japan's hydraulic drive, set up in 1956, "Hydraulic Industry." Nearly 20 to 30 years, the development of Japan's fast hydraulic transmission, a world leader. Hydraulic transmission There are many outstanding advantages, it is widely used, such as general workers. Plastic processing industry, machinery, pressure machinery, machine tools, etc.; operating machinery engineering machinery, construction machinery, agricultural machinery, automobiles, etc.; iron and steel industry metallurgical machinery, lifting equipment, such as roller adjustment device; civil water projects with flood control the dam gates and devices, bed lifts installations, bridges and other manipulation of institutions; speed turbine power plant installations, nuclear power plants, etc.; ship deck crane (winch), the bow doors, bulkhead valves, such as the stern thruster ; special antenna technology giant with control devices, measurement buoys, movements such as rotating stage; military-industrial control devices used in artillery, ship anti-rolling devices, aircraft simulation, aircraft retractable landing gear and rudder control devices and other devices. Hydraulic fluids are a large group of fluids used as the motive medium in hydraulic machinery. Fluid types include synthetic compounds, mineral oil, water, and water-based mixtures. The fluids are found in machinery and equipment ranging from brakes, power steering systems. Hydraulic systems are very common in aircraft flight control systems.Hydraulic systems like the ones mentioned above will work most efficiently if the hydraulic fluid used has low compressibility.Because industrial hydraulic systems operate at hundreds to thousands of PSI and temperatures reaching hundreds of degrees Celsius, severe injuries and death can result from component failures and care must always be taken when performing maintenance on hydraulic systems.Fire resistance is a property available with specialized fluids.The use of hydraulic systems in aircraft almost certainly began with braking systems.citation needed As aircraft performance increased in mid-20th century, the amount of force required to operate mechanical flight controls became excessive, and hydraulic systems were introduced to reduce pilot effort. The hydraulic actuators are controlled by valves; these in turn are operated directly by input from the aircrew (hydro-mechanical) or by computers obeying control laws (fly by wire). See flight controls.Hydraulic power is used for other purposes. It can be stored in accumulators to start an auxiliary power unit (APU) for self-starting the aircraft's main engines. Many aircraft equipped with the M61 family of cannon use hydraulic power to drive the gun system, permitting reliable high rates of fire.The hydraulic power itself comes from pumps driven by the engines directly, or by electrically driven pumps. Electric pumps can provide both redundancy and the means of operating hydraulic systems without starting the engines, which can be very useful during maintenance.Aircraft hydraulic fluids fall under various specifications:Exposure to hydraulic fluids occurs mainly in the workplace. Drinking certain types of hydraulic fluids can cause death in humans, and swallowing or inhaling certain types of hydraulic fluids has caused nerve damage in animals. Contact with some types of hydraulic fluids can irritate your skin or eyes. These substances have been found in at least 10 of the 1,428 National Priorities List sites identified by the Environmental Protection Agency (EPA).What is hydraulic fluids? Hydraulic fluids are a large group of liquids made of many kinds of chemicals. They are used in automobile automatic transmissions, brakes, and power steering; fork lift trucks; tractors; bulldozers; industrial machinery; and airplanes. The three most common types of hydraulic fluids are mineral oil, organophosphate ester, and polyalphaolefin. Some of the trade names for hydraulic fluids include Durad®, Fyrquel®, Skydrol®, Houghton-Safe®, Pydraul®, Reofos®, Reolube®, and Quintolubric®. (Use of trade names is for identification only and does not imply endorsement by the Agency for Toxic Substances and Disease Registry, the Public Health Service, or the U.S. Department of Health and Human Services.)Some hydraulic fluids have a bland, oily smell and others have no smell; some will burn and some will not burn. Certain hydraulic fluids are produced from crude oil and others are manufactured.What happens to hydraulic fluids when it enters the environment? Hydraulic fluids can enter the environment from spills, leaks in machines that use them, or from storage areas and waste sites. If spilled on soil, some of the ingredients in hydraulic fluids will stay on top and others will sink into the groundwater. In water, some hydraulic fluids' ingredients will transfer to the bottom and can stay there for more than a year. Certain chemicals in hydraulic fluids may break down in air, soil, or water, but how much breaks down isn't known. Fish may contain some hydraulic fluids if they live in contaminated water. How might I be exposed to hydraulic fluids? Touching or swallowing hydraulic fluids. Breathing hydraulic fluids in the air near machines where hydraulic fluids are used. Touching contaminated water or soil near hazardous waste sites or industrial manufacturing facilities that use or make hydraulic fluids. How can hydraulic fluids affect my health? Little is known about how hydraulic fluids can affect your health. Since hydraulic fluids are actually mixtures of chemicals, some of the effects seen may be caused by additives in the hydraulic fluids.In people, the effects of breathing air with high levels of hydraulic fluids are not known. Drinking large amounts of some types of hydraulic fluids can cause pneumonia, intestinal bleeding, or death in humans. Weakness of the hands was seen in a worker who touched a lot of hydraulic fluids.Rabbits that inhaled very high levels of one type of hydraulic fluid had trouble breathing, congested lungs, and became drowsy. The nervous systems of animals that swallowed or inhaled other hydraulic fluids were affected immediately with tremors, diarrhea, sweating, breathing difficulty, and sometimes several weeks later with weakness of the limbs, or paralysis. The immediate effects are caused because hydraulic fluids stop the action of certain enzymes, called cholinesterases, in the body. There are no reports of people swallowing or breathing the types of hydraulic fluids that cause these effects. When certain types of hydraulic fluids were put into the eyes of animals or allowed to touch the skin of people or animals for short periods of time, redness and swelling occurred. It is not known whether hydraulic fluids can cause birth defects or reproductive effects.Is there a medical test to show whether I've been exposed to hydraulic fluids? Hydraulic fluids can't be measured in blood, urine, or feces, but certain chemicals in the hydraulic fluids can be measured. Some of the hydraulic fluids stop the activity of certain enzymes, called cholinesterases, in blood and this activity can be measured. However, many other chemicals also cause this effect. This test isn't available at most doctors' offices, but can be done at special laboratories that have the right equipment.Has the federal government made recommendations to protect human health? There are no federal government recommendations to protect humans from the health effects of the major hydraulic fluids. However, mineral oil, the major chemical ingredient of one type of hydraulic fluid, is part of the petroleum distillate class of chemicals and there are regulations for these chemicals.The Occupational Safety and Health Administration (OSHA) has set an exposure limit of 2,000 milligram per cubic meter (mg/m³) petroleum distillates for an 8-hour workday, 40-hour workweek. The National Institute for Occupational Safety and Health (NIOSH) recommends an exposure limit of 350 mg/m³ petroleum distillates for a 10-hour workday, 40-hour workweek.Hydraulic technology has been the introduction of industry have a history of more than one hundred years. With the rapid development of industrial, hydraulic technology with each passing day. Along with mathematics, control theory, computers, electronic devices and the development of fluid mechanics, a hydraulic servo system. And as an applied science that has come of age, and form their own system and a well-established methods of analysis and design. The following is a method of hydraulic system design and attention to the problem:The based of Hydraulic design of hydraulic drive systemThe overall layout of the hydraulic machine and process requirements, including the use of hydraulic transmission by the type of machine, mechanical design made possible the implementation of the hydraulic components of the type and model, the implementation of components and their spatial position of the size range, the requirements of the degree of automation. The work of the hydraulic machine cycle, the executing agency of the movement, as well as the scope of work completed.Hydraulic velocity components, speed reference, travel, changes in the nature and scope of the load. The order of the parts and the interlocking action, as well as the work of the various components, such as the environment and area. Hydraulic system performance, such as stability, reliability, accuracy for the duration of time and out of traffic and other requirements. Other requirements, such as the quality of the hydraulic device, and economic dimensions, and so on 3, relief valve instability, such as slide-valve as a result of mis-match with the valve hole or conical valve contact with the valve seat is to be dirt stuck, damping plug holes, springs, etc. skew or failure in the valve spool jammed or hole Mobile not working, causing the system pressure fluctuations and noise. In this regard, should pay attention to cleansing, to clear the hole damping; check on relief valve, such as in case of damage, or in excess of wear and tear should be repaired or replaced in time; 4, valve adjusted properly, so that spool valve moving too fast, resulting in reversing the impact, resulting in noise and vibration. In this case, if the valve is a hydraulic valve, it should adjust the control circuit components of expenditure, so that the impact of exchange to non-smooth. At work, hydraulic spool valve support spring, when the oil pump frequency and the pulse rate frequency or with other similar local oscillator frequency will cause vibration, noise. At this time, by changing the natural frequency of the pipeline system, change the location of control valves to increase storage or appropriate, you can vibration noise. 5, mechanical vibration, such as thin tubing, and more without additional fixed bend in the flow of oil out of date, especially when a higher flow rate, it is easy to jitter caused by the tube; motor and hydraulic pump imbalances of the rotating part, or in the installation when in a bad or loose coupling and so on, can produce vibration and noise. Measures should be taken are: the longer the pipeline should be separated from each other and separated from the wall and machine, the appropriate folder to install pipe supports; adjustment of the hydraulic pump motor and the installation of precision; re-install the coupling to ensure that small coaxiality 0.1MM and so on. Hydraulic system installed in the pipeline, hydraulic components, hydraulic pump Notes How to clean the hydraulic system Hydraulic system in the manufacturing, testing, use and storage are subject to pollution, and cleaning is to eliminate pollution of hydraulic oil, hydraulic components and pipe cleaning, such as an important means to maintain. Production cleaning the hydraulic system usually have the main system and system-wide cleansing cleaning. System-wide cleansing refers to the hydraulic device for cleaning the entire loop in the pre-cleaning system should be restored to the actual functioning of the state. Medium can be used to clean hydraulic oil, cleaning time is normally 2-4 hours under special circumstances not more than 10 hours, cleaning effect of the loop filter as a standard without impurities. When cleaning the hydraulic system in general, the use of hydraulic oil used in the work or test the oil. Can not use kerosene, gasoline, alcohol, steam or other liquids, to prevent the hydraulic components, pipes, tanks and seals, such as by corrosion. In order to prevent external corrosion caused by moisture, cleaning at the end of the hydraulic pump but also continuous operation until the temperature returned to normal until after the cleaning circuit to rule out the possibility of cleaning the oil clean.Glossary Additive: Substance added to another in small amounts to improve its properties.CAS: Chemical Abstracts Service.Carcinogenicity: Ability to cause cancer.Petroleum Distillate: A chemical fraction of petroleum