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Comparison of the advantages and disadvantages of the four major transmission methods: mechanical, e

2020-02-20

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There are many ways of transmission. Of the four major types of transmission methods (mechanical, electrical, hydraulic, and pneumatic) that are currently in use, none of them are perfect. Today I will share with you the advantages and disadvantages of the four transmission methods.



First, mechanical transmission



Gear transmission


Gear transmission is the most widely used transmission form in mechanical transmission. Its transmission is relatively accurate, high efficiency, compact structure, reliable operation and long life. Gear transmission can be divided into many different types according to different standards.


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Advantage:

Compact structure, suitable for short-distance transmission; suitable for a wide range of peripheral speeds and powers; accurate, stable and efficient transmission ratio; high reliability and long life Between transmissions.


Disadvantages:

Requires higher manufacturing and installation accuracy, higher cost; not suitable for long distance transmission between two shafts; no overload protection.


2. Turbo worm drive

It is suitable for the motion and power between two axes that are perpendicular and not intersected in space.


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Advantages: large transmission ratio; compact size.

Disadvantages: large axial force, easy heating, low efficiency, only one-way transmission.

The main parameters of turbine worm gear transmission are: modulus; pressure angle; worm gear index circle; worm index circle; lead; worm gear number; worm head number; transmission ratio and so on.

3. Belt drive

Belt transmission is a kind of mechanical transmission using a flexible belt tensioned on a pulley for movement or power transmission. The belt drive usually consists of a driving wheel, a driven wheel, and an endless belt tensioned on two wheels.


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1) It is used in the occasion where the two axes are parallel to rotate in the same direction, which is called the concepts of opening movement, center distance and wrap angle.

2) The types of belts can be divided into three types: flat belts, V belts and special belts.

3) The key points in application are: calculation of transmission ratio; analysis and calculation of stress of belt; allowable power of single V-belt.

4) The main characteristics of belt drive:


Advantage:

It is suitable for the transmission with a large center distance between the two shafts. The belt has good flexibility, which can reduce impact and absorb vibration; it slips when overloaded to prevent damage to other parts.


Disadvantages:

The outer dimensions of the transmission are large; a tensioning device is required; due to slipping, a fixed transmission ratio cannot be guaranteed; the life of the belt is short; and the transmission efficiency is low.


4.Chain drive

Chain transmission is a transmission method that transmits the motion and power of a driving sprocket with a special tooth shape to a driven sprocket with a special tooth shape through a chain. Including active chain, driven chain, endless chain.


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Advantages: Chain drive has many advantages. Compared with belt drive, it has no elastic sliding and slipping. The average transmission ratio is accurate, the work is reliable, and the efficiency is high. The transmission power is large, the overload capacity is strong, and the transmission size under the same working conditions is small. It requires small tension and small pressure on the shaft; it can work in harsh environments such as high temperature, humidity, dust, and pollution.


Compared with gear transmission, chain transmission requires lower manufacturing and installation accuracy; when the center distance is large, its transmission structure is simple; instantaneous chain speed and instantaneous transmission ratio are not constant, and transmission stability is poor.


Disadvantages: The main disadvantages of chain transmission are: it can only be used for transmission between two parallel shafts; high cost, easy to wear, easy to extend, poor transmission stability, additional dynamic loads, vibration, shock and noise will be generated during operation, it is not suitable In rapid reverse drive.



5. Gear train

A transmission consisting of more than two gears is called a gear train. Gear transmission can be divided into ordinary gear transmission and planetary gear transmission according to whether gears with axis movement in the gear train. Gears with axis movement in the gear train are called planetary gears.


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1) The gear train is divided into two types: fixed axle gear train and epicyclic gear train.

2) The ratio of the angular velocity (or speed) of the input shaft to the output shaft in the gear train is called the gear train's transmission ratio. It is equal to the ratio of the product of the number of teeth of all driven gears and the product of the number of teeth of all driving gears in each pair of meshing gears.

3) In the epicyclic gear train, the gear whose axis position changes, that is, the gear which rotates both and revolves, is called planetary gear, and the gear with fixed axis position is called center gear or sun gear.

4) The transmission ratio of the epicyclic gear train cannot be directly calculated by solving the transmission ratio of the fixed-axis gear train. The principle of relative motion must be used to convert the epicyclic gear train into an imaginary one by using the relative speed method (or called the reverse method). Fixed-axis gear trains are calculated.

5) Main features of the gear train:

It is suitable for the transmission between two shafts that are far apart; it can be used as a transmission to realize variable speed transmission; a larger transmission ratio can be obtained;


Second, electrical transmission

Electrical transmission refers to the use of electric motors to convert electrical energy into mechanical energy to drive various types of production machinery, transportation vehicles, and items that need to be moved in life.

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1. High accuracy: The servo motor is used as the power source. It consists of a ball screw and a timing belt. Its repeat accuracy error is 0.01%.

2. Energy saving: The energy released during the deceleration phase of the working cycle can be converted into electric energy for reuse, thereby reducing the operating cost. The connected electrical equipment is only 25% of the electrical equipment required for hydraulic drive.

3. Precise control: Realize precise control according to the set parameters. With the support of high-precision sensors, measuring devices and computer technology, it can greatly exceed the control accuracy that can be achieved by other control methods.

4. Improve environmental protection level: Due to the reduction in the use of energy sources and its optimized performance, pollution sources have been reduced and noise has been reduced, which has provided a better guarantee for the environmental protection work of the factory.

5. Reduce noise: its operating noise value is less than 70 decibels, which is about 2/3 of the noise value of hydraulically driven injection molding machines.

6. Cost saving: This machine removes the cost and trouble caused by hydraulic oil, there is no hard pipe or soft hose, there is no need to cool the hydraulic oil, and the cost of cooling water is greatly reduced.

Three, pneumatic transmission

Pneumatic transmission is a fluid transmission that uses compressed gas as the working medium and transmits power or information by the pressure of the gas.

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Advantage:

1) Air is used as the working medium. The working medium is relatively easy to obtain. The used air is discharged into the atmosphere and is easy to handle. Compared with hydraulic transmission, there is no need to set up recycled oil tanks and pipes.

2) Because the viscosity of air is very small (about one ten-thousandth of the dynamic viscosity of hydraulic oil) and its loss is small, it is convenient for centralized air supply and long-distance transportation. External leaks do not pollute the environment as severely as hydraulic transmissions.

3) Compared with hydraulic transmission, pneumatic transmission has fast action, fast response, simple maintenance, clean working medium, and no problems such as medium deterioration.

4) Good adaptability to working environment, especially in harsh working environments such as flammable, explosive, dusty, strong magnetism, radiation, vibration, etc., superior to hydraulic, electronic, and electrical control.

5) Low cost, automatic protection for overload.


Disadvantages:

1) Due to the compressibility of air, the working speed stability is slightly worse. However, using gas-liquid linkage device will get more satisfactory results.

2) Because the working pressure is low (usually 0.31MPa) and the structure size should not be too large, the total output force should not be greater than 10 ~ 40kN.

3) Muffler is required for high-speed exhaust.

4) The air signal transmission speed in the pneumatic device is slower than the speed of electronics and light within the speed of sound. Therefore, the pneumatic control system should not be used for complex circuits with too many component stages.


Fourth, hydraulic transmission

Hydraulic transmission is a transmission method that uses liquid as the working medium to transfer energy and control.

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Advantage:

1) From a structural point of view, the output power per unit weight and output power per unit size are powerful in the four types of transmission methods, and have a large torque-inertia ratio. Under the condition of transmitting the same power, the hydraulic transmission device Small size, light weight, small inertia, compact structure and flexible layout.


2) From the perspective of working performance, speed, torque, and power can be adjusted steplessly. The action is fast in response, can quickly change direction and change speed, and has a wide range of speed adjustment, which can reach 100: 1 to 2000: 1; It is fast, easy to control and adjust, easy to operate and labor-saving, easy to cooperate with electrical control, and connected to a CPU (computer), and it is easy to realize automation.


3) From the perspective of use and maintenance, the components have good self-lubricity, easy to achieve overload protection and pressure retention, safe and reliable; components are easy to achieve serialization, standardization and generalization.


4) All equipment using hydraulic technology has good safety and reliability.


5) Economic: The plasticity and variability of hydraulic technology are very strong, which can increase the flexibility of flexible production, and easily change and adjust the production process. Relatively speaking, the manufacturing cost of hydraulic components is not high, and the adaptability is relatively strong.


6) The combination of easy hydraulic pressure and new technologies such as microcomputer control to form a "mechanical-electrical-hydraulic-optical" integration has become the trend of world development and facilitates digitalization.


Everything is divided into two, there are advantages and disadvantages, and hydraulic transmission is no exception:


Disadvantages:


1) Due to the relative motion surface of hydraulic transmission, leakage is unavoidable. At the same time, the oil is not absolutely incompressible. In addition to the elastic deformation of oil pipes, hydraulic transmission cannot obtain a strict transmission ratio, so it cannot be used for machine tools such as threaded gears Inline drive chain.


2) There are edge loss, local loss and leakage loss in the flow of oil, the transmission efficiency is low, and it is not suitable for long-distance transmission.


3) Under high and low temperature conditions, it is difficult to use hydraulic transmission.


4) In order to prevent oil leakage and meet certain performance requirements, the manufacturing precision of hydraulic components is high, which brings certain difficulties to use and maintenance.


5) Failures are not easy to check, especially for units where hydraulic technology is not very popular. This contradiction often hinders the further promotion and application of hydraulic technology. Hydraulic equipment maintenance requires certain experience, and it takes longer to train hydraulic technicians.