Feb. 02, 2021
At present, the widely used transmission methods mainly include mechanical transmission, electric transmission, pneumatic transmission and hydraulic transmission. Each has its own advantages and disadvantages. Mechanical transmission is driven by gears, racks, worms, worm gears, belts, chains, levers and other mechanical parts. It is an early developed and widely used transmission form. It has the advantages of accurate and reliable transmission, simple operation, intuitive and easy-to-master mechanism, small influence of load changes on transmission ratio and small environmental impact. However, in the case of automatic control, it is complicated and cumbersome to complete by mechanical transmission alone, and it has disadvantages such as difficult remote control, large operating force, and low degree of freedom for installation position changes. Therefore, it is gradually affected by other transmission methods in many occasions. replace.
Electric drive is driven and controlled by electricity. It uses AC motor to drive. It is simple and inexpensive, so it is widely used and is also a component of various transmissions. However, AC motors are generally difficult to perform continuously variable speed. Although DC motors can achieve infinitely variable speeds, DC power supplies are more expensive. The current thyristor technology greatly simplifies the stepless speed change of the AC motor, but the application in high-power, low-speed and high-torque applications still needs to be further improved. Electrical control, especially electronic computer control, has the advantages of convenient signal change and transmission, and easy remote operation. Therefore, it is suitable for occasions with high requirements for automation.
Pneumatic transmission uses compressed air as the transmission medium, and stepless speed can be easily achieved by adjusting the air volume. At the same time, it has the advantages of convenient transmission and conversion of signals, fast response, and simple structure. Moreover, the air is taken from the atmosphere, so the air source is cheap. Leakage can also be directly released into the atmosphere without causing pollution. The air viscosity is small, so the pipeline pressure loss is small, the flow rate is large, and high-speed motion can be obtained (such as a pneumatic grinding head above 100,000 revolutions per minute). But the fatal weakness of pneumatic transmission is that the air is highly compressible, and it cannot obtain uniform and stable movement. In addition, in order to reduce leakage, the pressure of the pneumatic system should not be too high, generally only about 0.7-0.8MPa. This makes it unsuitable for high-power applications.
Hydraulic systems have been more and more widely used in various industrial sectors and many sectors such as agriculture, forestry, animal husbandry and fishery, and the more advanced the equipment, the more hydraulic systems are used.
Hydraulic systems are widely used in light industry such as papermaking, textiles, plastics, rubber and other mechanical equipment such as paper machines, textile machines, injection molding machines, rubber briquetting machines, etc. In heavy industries such as mining, petroleum, metallurgy, and pressure processing, hydraulic systems can transmit a lot of energy and the weight of the equipment is relatively small compared to other transmission methods, so it has a wide range of applications. For example, hydraulic systems on equipment such as mine supports, oil drilling platforms, blast furnace roof equipment, billet continuous casters, strip mill reduction systems, presses, and fast forging machines are widely used. In the power, construction, water conservancy, transportation, shipbuilding, aviation, automotive and other industries, hydraulic systems are also an important part. As for the aerospace, military industry and other departments that widely adopt advanced technologies, hydraulic systems are widely used. The machine tool industry is one of the industries that have used hydraulic technology early. Although the motor drive has regained many applications of hydraulic drive due to the development of AC frequency conversion technology in the motor drive technology, the hydraulic system It is still widely used.
