Precision machinery-reducer principle and classification!
The reducer plays the role of matching the speed and transmitting torque between the prime mover and the working machine or the actuator. The reducer is an independent component composed of gear transmission, worm transmission, and gear-worm transmission enclosed in a rigid shell. It is often used as a reduction transmission device between the original moving part and the working machine. Generally used for low-speed and high-torque transmission equipment, the electric motor, internal combustion engine or other high-speed running power, through the gear on the input shaft of the reducer with a small number of teeth meshing with the large gear on the output shaft to achieve the purpose of deceleration, The gear ratio is the transmission ratio.
The reducer is a relatively precise machine. The purpose of using it is to reduce the speed and increase the torque. There are many types of reducers, with different models, and different types have different uses.
According to the transmission type, it can be divided into gear reducer, worm reducer and planetary gear reducer; according to the different transmission stages, it can be divided into single-stage and multi-stage reducers; according to the gear shape, it can be divided into cylindrical gear reducer and bevel gear reducer And conical-cylindrical gear reducer; according to the transmission layout, it can be divided into expansion, split and coaxial reducers.
In order to facilitate the reasonable selection of reducers, the types, characteristics and applications of several common reducers are listed one by one for reference when selecting models.
1. Single-stage cylindrical gear reducer Single-stage cylindrical gear reducer is suitable for reduction ratio 3~5. The gear teeth can be straight teeth, helical teeth or herringbone teeth. The box is usually cast iron or welded by steel plates. Rolling bearings are commonly used for bearings, and sliding bearings are only used for heavy loads or extremely high speeds.
2. Two-stage cylindrical gear reducer Two-stage cylindrical gear reducer is divided into three types: expansion type, split type and coaxial type, suitable for reduction ratio of 8-40.
Expanded type: high-speed long-tail helical gear, low-speed gear can be straight or helical gear. Due to the asymmetrical arrangement of the gear relative to the bearing, the rigidity of the shaft is required to be greater, and the torque input and output ends are far away from the gear to reduce the uneven load distribution along the tooth width caused by the bending deformation of the shaft. The structure is simple and the most widely used.
Shunt type: generally adopt high-speed grade shunt. Because the gear is arranged symmetrically with respect to the bearing, the force on the gear and the bearing is more even. In order to make the total axial force on the shaft smaller, the helix directions of the two pairs of gears should be opposite. The structure is more complicated, and is often used in places with high power and variable loads.
Coaxial type: The axial dimension of the reducer is larger, the intermediate shaft is longer, and the rigidity is poor. When the oil immersion depth of the two large gears is similar, the load-carrying capacity of the high-speed gear cannot be fully utilized. Commonly used in places where the input and output shafts are coaxial.
3. Single-stage bevel gear reducer Single-stage bevel gear reducer is suitable for reduction ratio 2~4. The transmission ratio should not be too large to reduce the size of the bevel gear and facilitate processing. It is only used in transmission where two axes intersect perpendicularly.
4. Cone and cylindrical gear reducers Cone and cylindrical gear reducers are suitable for reduction ratios of 8-15. The bevel gears should be arranged in the high-speed stage to reduce the size of the bevel gears. Bevel gears can be straight or curved teeth. Cylindrical gears are mostly helical teeth, which can offset part of the axial force of bevel gears.
5. Worm reducers mainly include cylindrical worm reducers, arc toroidal worm reducers, cone worm reducers and worm-gear reducers, among which cylindrical worm reducers are the most commonly used.
Worm reducer is suitable for reduction ratio of 10~80. The structure is compact, the transmission ratio is large, but the transmission efficiency is low, and it is suitable for the occasions of low power and gap work. When the peripheral speed of the worm is V≤4~5m/s, the worm is under-mounted, and the lubrication and cooling conditions are better; when V≥4~5m/s, the agitation loss of the oil is larger, and the worm is generally the upper-mounted type.
6. Planetary gear reducer Because of the structure of the planetary gear reducer, the minimum single-stage reduction is 3, generally not more than 10. The common reduction ratio is: 3/4/5/6/8/10, and the number of stages of the reducer generally does not exceed 3. , But some customized gearboxes with large reduction ratios have 4-stage reduction.
Compared with other reducers, planetary reducers have high rigidity, high precision (single-stage can be within 1 minute), high transmission efficiency (single-stage 97%-98%), high torque, volume ratio, lifetime maintenance-free, etc. Features. Because of these characteristics, planetary reducers are mostly installed on stepper motors and servo motors to reduce speed, increase torque, and match inertia.