Types and characteristics of common reducer

According to the type of transmission, 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 multistage reducers; According to the shape of the gear, it can be divided into cylindrical gear reducer, conical gear reducer and conical cylindrical gear reducer; According to the layout of transmission, it can be divided into deployable, shunting and concentric reducers.

In order to facilitate the rational selection of reducers, the types, characteristics and applications of several common reducers are listed one by one for reference in selection.

1. Single stage cylindrical gear reducer
Single stage cylindrical gear reducer is suitable for reduction ratios of 3 to 5. The gear teeth can be straight teeth, oblique teeth or herringbone teeth, and the box is usually cast in cast iron or welded with steel plates. Bearings are commonly used as rolling bearings, and sliding bearings are used only when heavy loads or ultrahigh speeds are used.

2. Two stage cylindrical gear reducer
There are three kinds of two-stage cylindrical gear reducers, namely, unfolding, shunting and concentric, which are suitable for reduction ratios of 8 to 40.
(1) Deployable: high-speed stage long tail oblique teeth, low-speed stage can be straight teeth or oblique teeth. Due to the asymmetric arrangement of the gear relative to the bearing, the rigidity of the shaft is required to be large, and the torque input and output ends are kept away from the gear to reduce the uneven distribution of load along the tooth width caused by the bending deformation of the shaft. The structure is simple and the application is the most extensive.
(2) Split type: high-speed split is generally used. Due to the symmetrical arrangement of gears relative to bearings, the forces on gears and shafts are more uniform. In order to reduce the total axial force on the shaft, the helixes of the two pairs of gears should be in the opposite direction. The structure is complex, which is often used in places with high power and variable load.
(3) Coaxiality: the axial dimension of the reducer is large, the intermediate shaft is long, and the rigidity is poor. When the oil immersion depth of the two large gears is similar, the bearing capacity of the high-speed gear can not be brought into full play. It is often used in places where the input and output shafts are on the same axis.

3. Single stage conical gear reducer
The single stage conical gear reducer is suitable for a reduction ratio of 2 to 4. The transmission ratio should not be too large to reduce the size of the conical gear and facilitate processing. Only in drives where two axes intersect vertically.

4. Taper and cylindrical gear reducer
Conical and cylindrical gear reducers are suitable for reduction ratios of 8 to 15. The taper gears shall be arranged in the high-speed stage to reduce the size of the taper gears. The taper gears can be straight teeth or curved teeth. Cylindrical gears are mostly skewed teeth, allowing them to offset part of the axial force of the conical gear.

5. Worm reducer
There are mainly cylindrical worm reducer, circular arc toroidal worm reducer, conical worm reducer and worm gear reducer, among which cylindrical worm reducer is the most commonly used.
The worm reducer is suitable for a reduction ratio of 10 to 80. Compact structure, large transmission ratio, but low transmission efficiency, suitable for small power, clearance work occasions. When the peripheral speed of the worm is v ≤ 4~5 m/s, the worm is lower, and the lubrication and cooling conditions are better; When v ≥ 4~5m/s, the stirring loss of oil is large, and the worm is generally upward.

6. Planetary gear reducer
Due to structural reasons, the minimum single stage deceleration of planetary reducer is 3, the maximum is generally not more than 10, the common deceleration ratio is 3/4/5/6/8/10, and the number of reducer stages is generally not more than 3, but some customized reducers with large deceleration ratio have 4 stages of deceleration.

Compared with other reducers, planetary reducers have the characteristics of high rigidity, high precision (single stage can achieve less than 1 point), high transmission efficiency (single stage is 97% - 98%), high torque, volume ratio and lifelong maintenance free. Because of these characteristics, planetary reducers are mostly installed on stepper motors and servo motors to reduce speed, increase torque and match inertia.