Among the current four major categories of transmission methods (mechanical, electrical, hydraulic and pneumatic), no power transmission is perfect.
Mechanical transmission
picture
1. Gear transmission
Including: plane gear transmission, space gear transmission.
advantage:
It has a wide range of applicable peripheral speeds and powers; the transmission ratio is accurate, stable and efficient; it has high working reliability and long service life; it can realize transmission between parallel axes, intersecting axes at any angle and staggered axes at any angle.
shortcoming:
Requires higher manufacturing and installation accuracy; higher cost; not suitable for transmission between two long-distance axes.
The names of the basic dimensions of involute standard gears include tooth tip circle, tooth root circle, index circle, modulus, pressure angle, etc.
2. Turbine worm drive
picture
Applicable to motion and dynamics between two axes that are vertical but not intersecting in space.
Advantages: large transmission ratio; compact structure and size.
shortcoming:
Large axial force; easy to generate heat; low efficiency; only one-way transmission.
The main parameters of the turbine worm drive are:
Module; pressure angle; worm gear pitch circle; worm pitch circle; lead; number of worm gear teeth; number of worm heads; transmission ratio, etc.
3. Belt drive
picture
Including: driving wheel, driven wheel, endless belt.
It is used when two axes are parallel and have the same rotation direction, which is called opening motion, the concepts of center distance and wrap angle. The types of belts can be divided into three categories according to their cross-sectional shapes: flat belts, V belts and special belts.
The key points during application are: calculation of transmission ratio; belt stress analysis and calculation; allowable power of a single V-belt.
advantage:
It is suitable for transmissions with a large center distance between two shafts; the belt has good flexibility, can alleviate impact and absorb vibration; it slips to prevent damage to other parts when overloaded; it has a simple structure and low cost.
shortcoming:
The outer size of the transmission is large; a tensioning device is required; a fixed transmission ratio cannot be guaranteed due to slippage; the belt life is short; and the transmission efficiency is low.
4. Chain drive
picture
Including: active chain, driven chain, and ring chain.
Compared with gear transmission, the main characteristics of chain transmission are: lower manufacturing and installation accuracy requirements; when the center distance is large, the transmission structure is simple; the instantaneous chain speed and instantaneous transmission ratio are not constant, and the transmission stability is poor.
5. Gear train
The gear train is divided into two types: fixed axis gear train and epicyclic gear train.
The ratio of the angular velocity (or rotational speed) of the input shaft and 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 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.
In the epicyclic gear system, the gears whose axis position changes, that is, the gears that rotate and revolve, are called planetary gears, and the gears whose axis position is fixed are called sun gears.
The transmission ratio of the epicyclic gear system cannot be calculated directly by the method of solving the transmission ratio of the fixed axis gear system. The principle of relative motion must be used to convert the epicyclic gear system into a hypothetical fixed axis by using the relative speed method (or called the inversion method). The wheel train is calculated.
The main features of the gear train: It is suitable for transmission between two axles that are far apart; it can be used as a transmission to achieve variable speed transmission; it can obtain a larger transmission ratio; it can realize the synthesis and decomposition of motion.
electric
picture
1. High accuracy
As a power source, the servo motor is a transmission mechanism with a simple structure and high efficiency, which is composed of a ball screw and a synchronous belt. Its repeatability error is 0.01%.
2. Save energy
The energy released during the deceleration phase of the working cycle can be converted into electrical energy for reuse, thereby reducing operating costs. The connected electrical equipment is only 25% of the electrical equipment required for hydraulic drive.
3. Precision control
Precise control is achieved based on set parameters. With the support of high-precision sensors, measuring devices, and computer technology, it can greatly exceed the control accuracy achieved by other control methods.
4. Improve environmental protection levels
Due to the reduction of energy types used and its optimized performance, pollution sources are reduced and noise is reduced, providing 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 a hydraulically driven injection molding machine.
6. Cost savings
This machine eliminates the cost and trouble caused by hydraulic oil. There are no hard pipes or flexible pipes, no need to cool the hydraulic oil, and the cost of cooling water is greatly reduced.
Hydraulic
picture
1.Advantages
1) From a structural point of view, its output power per unit weight and output power per unit size are the best among the four types of transmission methods. It has a large moment-to-inertia ratio. When transmitting the same power, the hydraulic transmission device is Small size, light weight, small inertia, compact structure and flexible layout.
2) From the perspective of working performance, the speed, torque and power can be adjusted steplessly, the action is responsive, the direction can be changed and speed changed quickly, the speed adjustment range is wide, and the speed adjustment range can reach 100:l to 2000:1; action It has good speed, relatively simple control and adjustment, convenient and labor-saving operation, and is easy to cooperate with electrical control and connect to CPU (computer) to facilitate automation.
3) From the perspective of use and maintenance, the components have good self-lubricating properties, are easy to achieve overload protection and pressure maintenance, and are safe and reliable; the components are easy to achieve serialization, standardization, and generalization.
4) All equipment using hydraulic technology has good safety and reliability.
5) Economy: Hydraulic technology has strong plasticity and variability, which can increase the flexibility of flexible production and make it easy to change and adjust production procedures. The manufacturing cost of hydraulic components is relatively low, and the adaptability is relatively strong.
6) Hydraulics can be easily combined with new technologies such as microcomputer control to form "mechanical-electronic-hydraulic-optical" integration, which has become a trend of world development and facilitates digitalization.
2. Disadvantages
Everything is divided into two parts, and hydraulic transmission is no exception.
1) Hydraulic transmission inevitably leaks due to relatively moving surfaces. At the same time, the oil is not absolutely incompressible. Coupled with the elastic deformation of oil pipes, etc., hydraulic transmission cannot obtain a strict transmission ratio, so it cannot be used for machine tools such as threaded gear processing. in the inline transmission chain.
2) There are edge losses, local losses and leakage losses in the oil flow process. The transmission efficiency is low and it is not suitable for long-distance transmission.
3) There are certain difficulties in using hydraulic transmission under high and low temperature conditions.
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) It is difficult to check when a fault occurs, especially in units where hydraulic technology is not widely used. This contradiction often hinders the further promotion and application of hydraulic technology. Hydraulic equipment maintenance requires experience, and training hydraulic technicians takes a long time.
air pressure
picture
1.Advantages
1) Using air as the working medium, it is relatively easy to obtain the working medium. 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 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 pollute the environment as seriously as hydraulic transmission.
3) Compared with hydraulic transmission, pneumatic transmission has fast action, quick response, simple maintenance, clean working medium, and no 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 magnetism, radiation, vibration, etc. It is superior to hydraulic, electronic and electrical controls.
5) Low cost, automatic overload protection.
2. Disadvantages
1) Since air is compressible, the working speed stability is slightly worse. However, the use of gas-liquid linkage device will achieve more satisfactory results.
2) Because the working pressure is low (generally 0.31.0MPa) and the structural size should not be too large, the total output force should not be greater than 10~40kN.
3) The noise is loud, so a muffler must 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 levels.
