Comparison of 4 major transmission methods: mechanical, electrical, pneumatic, hydraulic
There are many ways to drive. Among the four major types of transmissions (mechanical, electrical, hydraulic, and pneumatic) that are currently used, none of them are perfect. Today, I will share with you the advantages and disadvantages of the four transmission methods.
1. Mechanical transmission
Gear transmission
Gear transmission is the most widely used form of transmission in mechanical transmission. Its transmission is more accurate, high efficiency, compact structure, reliable operation and long service life. Gear drives can be divided into many different types according to different standards.
advantage:
Compact structure, suitable for short-distance transmission; applicable wide range of peripheral speed and power; accurate, stable and high transmission ratio; high reliability and long life; parallel axis, intersecting axis of arbitrary angle and staggered axis of any angle Drive between.
Disadvantages:
High manufacturing and installation accuracy and high cost are required; it is not suitable for transmission between two axes at a long distance; no overload protection.
2. Turbine worm drive
Suitable for motion and power between two axes with vertical and non-intersecting spaces.
Advantages: large transmission ratio; compact size.
Disadvantages: large axial force, easy to heat, low efficiency, only one-way transmission.
The main parameters of the turbine vortex drive are: modulus; pressure angle; worm wheel indexing circle; worm indexing circle; lead; worm gear number; worm head number; transmission ratio.
3. Belt drive
A belt drive is a mechanical transmission that utilizes a flexible belt that is tensioned on a pulley for motion or power transmission. The belt drive usually consists of a drive wheel, a driven wheel and an endless belt that is tensioned on the two wheels.
1) For the case where the direction of parallel rotation of two axes is the same, it is called the concept of opening motion, center distance and wrap angle.
2) The type of belt can be divided into three categories according to the cross-sectional shape: flat belt, V belt and special belt.
3) The application focuses on the calculation of the transmission ratio; the stress analysis calculation of the belt; the allowable power of the single V-belt.
4) Main features of the belt drive:
advantage:
It is suitable for transmission with large center distance between two shafts. It has good flexibility, can mitigate shock and absorb vibration. It can prevent damage to other parts when it is overloaded. It has simple structure and low cost.
Disadvantages:
The outer dimensions of the transmission are large; the tensioning device is required; the fixed transmission ratio cannot be guaranteed due to the slip; the life of the belt is short; the transmission efficiency is low.
4. Chain drive
The chain drive is a transmission method in which the movement and power of a drive sprocket having a special tooth shape is transmitted to a driven sprocket having a special tooth shape through a chain. Including active chain, driven chain, circular chain.
Advantages: The chain drive has many advantages. Compared with the belt drive, it has no elastic sliding and slipping phenomenon, the average transmission ratio is accurate, the work is reliable, and the efficiency is high; the transmission power is large, the overload capability is strong, and the transmission size under the same working condition is small; The tension is small, the pressure on the shaft is small, and it can work in harsh environments such as high temperature, humidity, dust, and pollution.
Compared with the gear transmission, the chain drive requires lower manufacturing and installation accuracy; when the center distance is larger, the transmission structure is simple; the instantaneous chain speed and the instantaneous transmission ratio are not constant, and the transmission stability is poor.
Disadvantages: The main disadvantages of chain drive are: only can be used for transmission between two parallel shafts; high cost, easy to wear, easy to stretch, poor transmission stability, additional dynamic load, vibration, shock and noise during operation, not suitable In the fast reverse drive.
5. Wheel train
A transmission consisting of more than two gears is called a train. According to whether the gear has axial movement in the train wheel, the gear transmission can be divided into ordinary gear transmission and planetary gear transmission, and the gear with axial movement in the train wheel is called a planetary gear.
1) The wheel train is divided into two types: fixed axle train and epicyclic train.
2) The ratio of the angular velocity (or rotational speed) of the input shaft to the output shaft in the train is called the gear ratio of the train. The ratio of the product of the number of teeth of all the driven gears in each pair of meshing gears to the product of the number of teeth of all the driving gears.
3) In the epicyclic gear train, the gear whose axis position changes, that is, the gear that is both rotated and revolved, is called a planetary gear, and the gear with a fixed axial position is called a center wheel or a sun gear.
4) The gear ratio of the epicyclic gear train cannot be directly calculated by the method of solving the fixed axle train ratio. The relative motion method (or inversion method) must be used to convert the epicyclic gear train into imaginary. The fixed axle train is calculated.
5) Main features of the train:
It is suitable for transmission between two axes that are far apart; it can be used as a transmission to realize variable speed transmission; a larger transmission ratio can be obtained; and the synthesis and decomposition of motion can be realized.
Electric drive
Electric drive 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.
1. High precision: The servo motor is used as the power source, and the ball screw and the timing belt are composed of a simple and efficient transmission mechanism. Its repeatability error is 0.01%.
2. Energy saving: The energy released in the deceleration phase of the working cycle can be converted into electric energy for reuse, thereby reducing the running cost, and the connected electric equipment is only 25% of the electric equipment required for hydraulic driving.
3, precision control: according to the set parameters to achieve precise control, with high-precision sensors, metering devices, computer technology support, can greatly exceed the control accuracy that other control methods can achieve.
4. Improving the level of environmental protection: Due to the reduction of energy use and its optimized performance, the pollution source is reduced and the noise is reduced, which provides a better guarantee for the environmental protection work of the factory.
5. Reduce noise: The operating noise value is less than 70 decibels, which is about 2/3 of the noise value of the hydraulically driven injection molding machine.
6. Cost saving: This machine removes the cost of hydraulic oil and causes trouble. There is no hard pipe or soft throat, no need to cool the hydraulic oil, and greatly reduce the cost of cooling water.
Three. Pneumatic transmission
Pneumatic transmission uses compressed gas as the working medium, and the fluid transmission of power or information by the pressure of the gas.
advantage:
1) With air as the working medium, the working medium is relatively easy to obtain, and the used air is discharged to the atmosphere, which is convenient to handle, and it is not necessary to set the recovered fuel tank and pipeline compared with the hydraulic transmission.
2) Because the viscosity of air is very small (about one ten thousandth of the dynamic viscosity of hydraulic oil), its loss is also small, so it is convenient to concentrate gas supply and transport at a long distance. External leaks do not pollute the environment as much as hydraulic drives.
3) Compared with the hydraulic transmission, the pneumatic transmission has quick action, fast response, simple maintenance, clean working medium, and no problem of deterioration of the medium.
4) The working environment has good adaptability, especially in the harsh working environment such as flammable, explosive, dusty, strong magnetic, radiation, vibration, etc., superior to hydraulic, electronic and electrical control.
5) The cost is low and the overload can be automatically protected.
Disadvantages:
1) Since the air is compressible, the working speed stability is slightly poor. However, the use of gas-liquid linkage device will get satisfactory results.
2) Due to low working pressure (generally 0.31 MPa), and because the structure size should not be too large, the total output force should not be greater than 10 ~ 40kN.
3) The noise is large, and the muffler should be added during high-speed exhaust.
4) The gas signal transmission speed in the pneumatic device is slower than the electron and light speed within the sound velocity. Therefore, the pneumatic control system should not be used in complex circuits with too many component stages.
Hydraulic drive
Hydraulic drives are transmissions that use liquid as a working medium to transfer energy and control.
advantage:
1) From the structural point of view, the output power per unit weight and the output power per unit size are force-compressed in the four types of transmission modes, and there is a large moment 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 work performance, the speed, torque and power can be adjusted steplessly, the action response is fast, the speed can be changed quickly and the speed is changed, the speed regulation range is wide, and the speed regulation range can reach 100:1 to 2000:1; The speed is good, the control and adjustment are relatively simple, the operation is convenient and labor-saving, and it is convenient to cooperate with the electric control and the connection with the CPU (computer) to facilitate automation.
3) From the point of view of use and maintenance, the self-lubricity of components is good, and it is easy to realize overload protection and pressure keeping, which is safe and reliable; components are easy to realize serialization, standardization and generalization.
4) All equipment using hydraulic technology is safe and reliable.
5) Economy: The plasticity and variability of hydraulic technology are very strong, which can increase the flexibility of flexible production, and it is easy to change and adjust the production process. The hydraulic components are relatively low in manufacturing cost and relatively adaptable.
6) The combination of hydraulic technology and new technologies such as microcomputer control constitutes the “machine-electric-liquid-light†integration, which has become the trend of world development and is easy to realize digitalization.
Everything is divided into two, with advantages and disadvantages. Hydraulic drives are no exception:
Disadvantages:
1) The hydraulic transmission is inevitably leaked due to the relative moving surface. At the same time, the oil is not absolutely incompressible. In addition to the elastic deformation of the oil pipe, the hydraulic transmission cannot obtain a strict transmission ratio, and thus cannot be used for machine tools such as threaded gears. In the inline drive chain.
2) There are loss along the loss, local loss and leakage during the flow of oil, the transmission efficiency is low, and it is not suitable for long-distance transmission.
3) Under high temperature and low temperature conditions, there are certain difficulties in using hydraulic transmission.
4) In order to prevent oil leakage and to meet certain performance requirements, the manufacturing accuracy of hydraulic components is high, which brings certain difficulties to use and maintenance.
5) It is difficult to check for faults, especially for units where hydraulic technology is not popular. This contradiction often hinders the further promotion and application of hydraulic technology. Hydraulic equipment maintenance requires a certain amount of experience, training hydraulic technicians for a longer period of time.
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