Comparison of the advantages and disadvantages of mechanical, electrical, hydraulic and pneumatic transmission methods

Editor's note: There are many types of transmission methods. Among the four most commonly used transmission methods (mechanical, electrical, hydraulic and pneumatic), no power transmission is perfect. Today I will share with you the advantages and disadvantages of the four transmission methods.

Mechanical transmission

1. Gear transmission

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

advantage:

The structure is compact and suitable for short-distance transmission; it is applicable to a wide range of circumferential speeds and power; the transmission ratio is accurate, stable and efficient; it has high working reliability and long service life; it can realize transmission between parallel axes, axes intersecting at any angle and axes staggered at any angle.

shortcoming:

It requires high manufacturing and installation precision and has high cost; it is not suitable for transmission between two shafts over a long distance; it has no overload protection function.

2. Turbine and worm gear drive

Applicable to the movement and dynamics between two perpendicular and non-intersecting axes in space.

Advantages: large transmission ratio; compact structure.

Disadvantages: large axial force, easy to heat up, low efficiency, and can only transmit in one direction.

The main parameters of turbine worm gear transmission are: module; pressure angle; worm wheel pitch circle; worm pitch circle; lead; number of worm wheel teeth; number of worm heads; transmission ratio, etc.

3. Belt drive

Belt drive is a kind of mechanical transmission that uses a flexible belt stretched on a pulley to transmit motion or power. Belt drive usually consists of a driving pulley, a driven pulley and an endless belt stretched on the two pulleys.

1) Used when two axes are parallel and rotate in the same direction, it is called opening motion, the concepts of center distance and wrap angle.

2) Belt types can be divided into three categories according to the cross-sectional shape: flat belts, V-belts and special belts.

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

4) Main features of belt drive:

advantage:

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

shortcoming:

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

4. Chain drive

Chain drive 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. It includes driving chain, driven chain and endless chain.

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

Compared with gear transmission, chain transmission has lower requirements for manufacturing and installation precision; when the center distance is large, its transmission structure is simple; the instantaneous chain speed and instantaneous transmission ratio are not constants, and the transmission smoothness is poor.

Disadvantages: The main disadvantages of chain drive are: it can only be used for transmission between two parallel shafts; it is costly, easy to wear, easy to stretch, has poor transmission stability, will generate additional dynamic loads, vibration, impact and noise during operation, and is not suitable for use in rapid reverse transmission.

5. Gear train

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

1) Gear trains are divided into two types: fixed-axis gear trains and epicyclic gear trains.

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

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

4) The transmission ratio of the epicyclic gear train cannot be directly calculated using the method for solving the transmission ratio of the fixed-axis gear train. It is necessary to utilize the principle of relative motion and use the relative velocity method (also called the inversion method) to transform the epicyclic gear train into an imaginary fixed-axis gear train for calculation.

5) Main features of the gear train:

It is suitable for transmission between two shafts that are far apart; it can be used as a transmission to achieve variable speed transmission; it can obtain a larger transmission ratio; and it can achieve the synthesis and decomposition of motion.

Electric Drive

Electric 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 objects that need to move in life.

1. High precision: The servo motor is used as the power source, and the transmission mechanism composed of ball screw and synchronous belt is simple in structure and highly efficient. Its repeatability error is 0.01%.

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

3. Precision control: Precise control can be achieved according to the set parameters. With the support of high-precision sensors, metering devices, and computer technology, the control accuracy can be greatly exceeded by other control methods.

4. Improve environmental protection level: Due to the reduction in the types of energy used and its optimized performance, the pollution sources are reduced and the noise is reduced, providing a better guarantee for the factory's environmental protection work.

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

6. Cost saving: This machine eliminates the cost and trouble of hydraulic oil, has no hard pipes or soft pipes, does not require hydraulic oil cooling, and greatly reduces cooling water costs.

Pneumatic transmission

Pneumatic transmission is a fluid transmission that uses compressed gas as the working medium and relies on the pressure of the gas to transmit power or information.

advantage:

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

2) Since the viscosity of air is very small (about one ten-thousandth of the dynamic viscosity of hydraulic oil), its loss is also very small, so it is convenient for centralized air supply and long-distance transportation. External leakage will not seriously pollute the environment like hydraulic transmission.

3) Compared with hydraulic transmission, pneumatic transmission is quick in action, quick in response, simple in maintenance, has clean working medium, and does not have problems such as medium deterioration.

4) It has good adaptability to the working environment, especially in harsh working environments such as flammable, explosive, dusty, strong magnetic, radiation, vibration, etc., which is superior to hydraulic, electronic, and electrical control.

5) Low cost and automatic overload protection.

shortcoming:

1) Since air is compressible, the working speed stability is slightly poor. However, a more satisfactory effect can be obtained by using a gas-liquid linkage device.

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

3) The noise is relatively loud, so a muffler should be added when exhausting at high speed.

4) The transmission speed of gas signals in pneumatic devices is slower than the speed of electrons and light within the speed of sound. Therefore, pneumatic control systems should not be used in complex circuits with too many component stages.

Hydraulic transmission

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

advantage:

1) From a structural point of view, its output power per unit weight and unit size are the best among the four types of transmission methods, and it has a large torque-to-inertia ratio. When transmitting the same power, the hydraulic transmission device has a small size, light weight, small inertia, compact structure and flexible layout.