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The most widely used transmission form in mechanical transmission2
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Advantages: chain drive has many advantages. Compared with belt drive, 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 fast reverse transmission.
5. Gear train
A transmission composed of more than two gears is called a gear train. 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 the tooth numbers of all driven gears in each pair of meshing gears to the product of the tooth numbers of all driving gears.
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 center gears or sun gears.
4) The transmission ratio of the epicyclic gear train cannot be directly calculated 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). Calculate with fixed-axis gear train.
5) The main features of the gear train:
It is suitable for the transmission between two shafts far apart; it can be used as a transmission to realize variable speed transmission; it can obtain a larger transmission ratio; it can realize the synthesis and decomposition of motion.
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 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 electrical 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: Accurate control is achieved 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, the pollution sources are reduced and the noise is reduced, which provides a better guarantee for the environmental protection work 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, and the cost of cooling water is greatly reduced.
Pneumatic transmission
Pneumatic transmission uses compressed gas as the working medium and transmits power or information by the pressure of the gas.
advantage:
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 adaptability to the working environment, 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 size of the structure should not be too large, the total output force should not be greater than 10-40kN.
3) The noise is 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.
Hydraulic transmission
Hydraulic transmission is a transmission method that uses 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 overwhelming among the four types of transmission modes, with a large moment-to-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) In terms of working performance, 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; action 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 retention, safe and reliable; components are easy to achieve serialization, standardization, and generalization.
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