There are many transmission modes. Among the four major types of transmission methods (mechanical, electrical, hydraulic, and pneumatic) that are currently widely used, none of the power transmissions is perfect. Today I will share with you the comparison of the pros and cons of the 4 transmission methods.
Mechanical transmission
1. Gear transmission
Gear transmission is the most widely used transmission form in mechanical transmission. It has relatively accurate transmission, high efficiency, compact structure, reliable work and long life. Gear transmission can be divided into many different types according to different standards.
Advantages:
compact structure, suitable for short-distance transmission; suitable for a wide range of circumferential speed and power; accurate, stable, and high-efficiency transmission ratio; high reliability and long life; it can realize parallel axis, intersecting axis at any angle and staggered at any angle Transmission between shafts.
Disadvantages:
higher manufacturing and installation accuracy, higher cost; not suitable for long-distance transmission between two shafts; no overload protection.
2. Turbine worm drive
Turbine worm drive is suitable for movement and power between two shafts where the space is vertical but not intersecting.
Advantages: large transmission ratio; compact structure size.
Disadvantages: large axial force, easy to heat, low efficiency, only one-way transmission.
The main parameters of the turbine worm drive are: modulus; pressure angle; worm gear index circle; worm index circle; lead; number of worm gear teeth; number of worm heads; transmission ratio.
3. Belt drive
Belt drive is a mechanical drive that uses a flexible belt tensioned on a pulley to transmit motion or power. The belt drive usually consists of a driving wheel, a driven wheel and an endless belt tensioned on two wheels.
1) It is used in the situation where the two axes are parallel to the same rotation direction, which is called the concept of opening movement, center distance and wrap angle.
2) The belt type can be divided into three categories: flat belt, V belt and special belt according to the cross-sectional shape.
3) The focus of application is: calculation of transmission ratio; stress analysis and calculation of belt; allowable power of a single V belt.
Advantages:
It is suitable for transmission with a large center distance between two axles. The belt has good flexibility, can relieve impact and absorb vibration; slip when overloaded to prevent damage to other parts; simple structure and low cost.
Disadvantages:
the outer size of the transmission is large; a tensioning device is required; due to slipping, a fixed transmission ratio cannot be guaranteed; the belt life is short; the transmission efficiency is low.
4. Chain drive
Chain drive is a transmission method in which the movement and power of a driving sprocket with a special tooth profile is transmitted to a driven sprocket with a special tooth profile through a chain. Including driving chain, driven chain, circular chain.
Advantages: Chain transmission has many advantages. Compared with belt transmission, there is 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 capacity is strong, and the transmission size under the same working condition is small; The need for tension is small and the pressure acting on the shaft is small; it can work in harsh environments such as high temperature, humidity, dust, and pollution.
Compared with gear transmission, chain drive requires lower manufacturing and installation accuracy; when the center distance is large, its transmission structure is simple; the instantaneous chain speed and instantaneous transmission ratio are not constant, and the 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 load, vibration, impact and noise during operation, it is not suitable for use In a rapid reverse transmission.
The gear transmission can be divided into ordinary gear transmission and planetary gear transmission according to whether there are gears with axis movement in the gear train. The gears with axis movement in the gear train are called planetary gears.
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 rotation speed) of the input shaft to the output shaft in the gear train is called the transmission ratio of the gear train. It is equal to the ratio of the product of all driven gear teeth in each pair of meshing gears to the product of all driving gear teeth.
3) In the epicyclic gear train, the gears whose axis position changes, that is, the gears that both rotate and revolve, are called planetary gears, and the gears with fixed axis positions are called sun gears.
4) The transmission ratio of the epicyclic gear train cannot be calculated directly by the method of solving the transmission ratio of the fixed-axis gear train. The principle of relative motion must be used to transform the epicyclic gear train into a hypothetical one using the relative speed method (or reversal method). The fixed-axis gear train is calculated.
5) The main characteristics of the gear train:
suitable for transmission between two shafts that are far apart; can be used as a transmission to achieve variable speed transmission; obtain a larger transmission ratio; realize movement synthesis and decomposition.
5. Electrical drive
Electrical 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 objects that need to be moved in life.
1. High accuracy: Servo motor is used as the power source, which is composed of a ball screw and a synchronous belt to form a simple and highly efficient transmission mechanism. 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 operating costs. 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, metering devices, and computer technology, it can greatly exceed the control accuracy that other control methods can achieve.
4. Improve the level of environmental protection: due to the reduction in the types of energy used and the optimized performance, pollution sources are reduced and noise is reduced, which provides a better guarantee for the environmental protection of the factory.
5. Noise reduction: 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 caused by hydraulic oil. There is no hard pipe or hose, no need to cool the hydraulic oil, which greatly reduces the cost of cooling water.
6. Pneumatic transmission
Pneumatic transmission uses compressed gas as the working medium and transmits power or information by the pressure of the gas.
Advantages:
1) With air as the working medium, it is easier to obtain the working medium, and the used air is discharged into the atmosphere, which is convenient to handle. Compared with hydraulic transmission, there is no need to set up a recovery oil tank and pipeline.
2) Because 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 pollute the environment as seriously as hydraulic transmission.
3) Compared with hydraulic transmission, pneumatic transmission has rapid action, quick response, simple maintenance, clean working medium, and no problems such as medium deterioration.
4) Good working environment adaptability, especially in the harsh working environment such as flammable, explosive, dusty, strong magnetism, radiation, vibration, etc., superior to hydraulic, electronic and electrical control.
5) Low cost, automatic overload protection.
Disadvantages:
1) Due to the compressibility of air, the stability of working speed is slightly worse. However, the gas-liquid linkage device will get a more satisfactory effect.
2) Due to the low working pressure (usually 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 large, and a muffler should be added when exhausting at high speed.
4) The air signal transmission speed in the pneumatic device is slower than the electron and light speed within the speed of sound. Therefore, the pneumatic control system is not suitable for complex circuits with too many components.
7. Hydraulic transmission
Hydraulic transmission is a transmission method that uses liquid as a working medium to transfer energy and control.
Advantages:
1) From the structural point of view, the output power per unit weight and output power per unit size are superior to the four types of transmission modes, with a large moment of inertia ratio. Under the condition of transmitting the same power, hydraulic transmission The device has small size, light weight, small inertia, compact structure and flexible layout.
2) In terms of working performance, the speed, torque and power can be adjusted steplessly, with fast action response, quick reversing and speed change, wide speed adjustment range, and the speed adjustment range can reach 100:1 to 2000:1; The speed is good, the control and adjustment are relatively simple, the operation is relatively convenient and labor-saving, it is convenient to cooperate with the electrical control, and the connection with the CPU (computer) is convenient to realize automation.
3) From the perspective of use and maintenance, the components have good self-lubrication, easy to achieve overload protection and pressure holding, safe and reliable; components are easy to achieve serialization, standardization, and generalization.
4) All equipment using hydraulic technology is safe and reliable.
5) Economy: The plasticity and variability of hydraulic technology is very strong, which can increase the flexibility of flexible production, and is easy to change and adjust the production process. The manufacturing cost of hydraulic components is relatively low, and the adaptability is relatively strong.
6) The combination of hydraulic pressure and microcomputer control and other new technologies to form a “mechanical-electric-hydraulic-optical” integration has become the trend of world development, which is convenient for digitalization.
Everything is divided into two, with advantages and disadvantages. Hydraulic transmission is no exception:
Disadvantages:
1) Hydraulic transmission is inevitably leaking due to relative moving surfaces. 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. Used in the inline drive chain of machine tools such as processing threaded gears.
2) There are edge losses, local losses and leakage losses in the process of oil flow, and the transmission efficiency is low, which is not suitable for long-distance transmission.
3) Under high temperature and low temperature conditions, it is difficult to use hydraulic transmission.
4) In order to prevent oil leakage and meet certain performance requirements, hydraulic components require high manufacturing precision, which brings certain difficulties to use and maintenance.
5) Failure to check is not easy, especially in 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, and it takes a long time to train hydraulic technicians.