Four mechanical transmissions, who is the king of transmission!
Four mechanical transmissions, who is the king of transmission!
Among the current four major types of transmission (mechanical, electrical, hydraulic and pneumatic), none of the power transmissions is perfect.
一: Machinery
1. Gear transmission includes: flat gear transmission and space gear transmission.
Advantages: Wide range of applicable peripheral speed and power; accurate, stable and high transmission ratio; high reliability and long life; can realize transmission between parallel axis, intersecting axis of arbitrary angle and staggered axis of arbitrary angle.
Disadvantages: high manufacturing and installation accuracy; high cost; not suitable for transmission between two axes at a long distance. The basic dimensions of the involute standard gear are the tip circle, the root circle, the index circle, the number of touches, the pressure angle, and the like.
2, turbine vortex drive: suitable for the movement and power between the two axes of vertical and non-intersecting space.
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: including: drive wheel, driven wheel, ring belt. 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. The type of belt can be divided into three categories according to the cross-sectional shape: flat belt, V belt and special belt. The application focuses on the calculation of the gear ratio; the stress analysis calculation of the belt; the allowable power of the single V-belt.
Advantages: It is suitable for transmission with large center distance between two shafts; belt has good flexibility, can mitigate impact and absorb vibration; slip during overload to prevent damage to other parts; simple structure and low cost.
Disadvantages: The outer dimensions of the transmission are large; the tensioning device is required; due to the slip, the fixed transmission ratio cannot be guaranteed; the life of the belt is short; the transmission efficiency is low.
4. Chain drive includes: active chain, driven chain and circular chain.
Compared with the gear transmission, the main characteristics of the chain drive are: low manufacturing and installation accuracy; when the center distance is large, the transmission structure is simple; the instantaneous chain speed and the instantaneous transmission ratio are not constant, and the transmission stability is poor.
5. Wheel train: The wheel train is divided into two types: fixed axle train and revolving train. 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. 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. 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 an imaginary fixed axis. The wheel train is calculated.
The main features of the train: suitable for transmission between two axes that are far apart; can be used as a transmission to achieve variable speed transmission; can obtain a larger transmission ratio; achieve the synthesis and decomposition of motion
二, electrical
1. High precision: 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 can be achieved by other control methods.
4. Improve 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 savings: This machine removes the cost of hydraulic oil and the trouble caused, there is no hard pipe or soft throat, no need to cool the hydraulic oil, greatly reducing the cost of cooling water.
三, hydraulic
1. Advantages: 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 The device is small in size, light in weight, small in inertia, compact in structure and flexible in layout. From the performance point of view, speed, torque, power can be steplessly adjusted, fast response, fast commutation and shifting, wide speed range, speed range up to 100: l to 2000:1; Well, the control and adjustment are relatively simple, the operation is convenient and labor-saving, and it is convenient to cooperate with the electrical control, and the connection with the CPU (computer) to facilitate automation. From the point of view of use and maintenance, the components have good self-lubricating properties, easy to achieve overload protection and pressure keeping, safe and reliable; components are easy to achieve serialization, standardization and generalization. All equipment with hydraulic technology is safe and reliable. Economy: The plasticity and variability of hydraulic technology is very strong, which can increase the flexibility of flexible production, and easy to change and adjust the production process. Hydraulic components are relatively inexpensive to manufacture and have relatively high adaptability. 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.
2. Disadvantages: Everything is divided into two, and hydraulic transmission is no exception. The hydraulic transmission is inevitably leaked due to the relative moving surface, and the oil is not absolutely incompressible. In addition, the hydraulic transmission can not obtain a strict transmission ratio, and thus cannot be used in machine tools such as threaded gears. In the transmission chain. There are loss along the loss, local loss and leakage during the flow of oil, and the transmission efficiency is low, which is not suitable for long-distance transmission. Under high temperature and low temperature conditions, hydraulic transmission has certain difficulties. In order to prevent oil leakage and to meet certain performance requirements, hydraulic components are manufactured with high precision requirements, which poses certain difficulties for use and maintenance. 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 relies on experience and trains hydraulic technicians for a longer period of time.
四, the air pressure
1. Advantages: 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. Because the viscosity of air is very small (about one ten-thousandth of the viscosity of hydraulic oil), its loss is also small, so it is convenient to concentrate gas supply and long-distance transportation. External leaks do not pollute the environment as much as hydraulic drives. Compared with the hydraulic transmission, the pneumatic transmission has a quick action, fast response, simple maintenance, clean working medium, and no deterioration of the medium. 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. The cost is low and the overload can be automatically protected.
2. Disadvantages: Due to the compressibility of air, the working speed stability is slightly poor. However, the use of gas-liquid linkage device will get satisfactory results. Due to low working pressure (generally 0.31.0MPa), and because the structure size should not be too large, the total output force should not be greater than 10 ~ 40kN. The noise is large, and a muffler is added at the time of high-speed exhaust. 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.
