1.Selection factor


1.1 Input power, output torque

The conversion formula of input power and output torque is as follows:

Input power P(kw)=output torque T(N.m)x output shaft speed N2(r/min)/( 9549x efficiency n )

The input power of the reducer is the input power capacity of the reducer, and the output torque is the allowable load capacity of the reducer. They are listed in the “Power, Torque” table of the product, which can be used for selection.


1.2 Input shaft speed, output shaft speed

The conversion formula of the input shaft and output shaft speed is as follows:

Output shaft speed N2 (r / min) = input shaft speed N, (r / min) / transmission ratio i

When the reducer is driven by pulley, sprocket and coupling, the input shaft speed should not exceed 2000 (r/min), the general speed range is 600-1800 (r/min), and the high speed will make the bearing increase friction and shorten the life. .


1.3 effectiveness

The efficiency calculation formula is as follows:

Efficiency n = (output power / input power) xioo%

Due to the friction and vibration inside the reducer, some of the input energy will be converted into non-working consumption such as heat. The efficiency is the utilization of the input energy of the reducer. The efficiency depends on the number of worm heads, the speed of the worm, the viscosity of the lubricating oil, and the bearing. Frictional resistance and friction coefficient of worm gear material. The speed reducer of each specification and transmission ratio has different efficiency values. The following table lists the range of efficiency values, which can be used for selection.:


Speed ratio 1/10 1/15 1/20 1/25 1/30 1/40 1/50 1/60
Effectiveness 77-90% 76-88% 75-84% 72-82% 68-82% 64-75% 62-72% 60-71%


1.4 Input shaft, output shaft rotation direction

The direction of rotation of the output shaft of the worm reducer depends on the direction of the worm thread, and the basic type worm reducer is a right-handed screw. Based on the WPA photos on the company's product samples, facing the input shaft and output shaft, when the input shaft rotates clockwise, the output shaft rotates counterclockwise; based on the WPS photo, the input shaft and output shaft When the input shaft rotates clockwise, the output shaft rotates clockwise; the remaining various output shaft assembly structures can be steered as described above. When left-handed in the direction of the special worm thread, the opposite is true.


1.5 Working condition coefficient

When the reducer is designed, the input power capacity and the allowable load capacity are calculated according to the ideal working condition of continuous operation for eight hours and the load is stable. In actual use, the on-site working conditions (such as whether there are repeated Start stop or frequent forward and reverse, whether the use time is less than or more than eight hours, the impact load size and characteristics) may be far from the ideal working condition, should be fully considered in the selection, in the selection of the reducer input power or When the torque is output, it can be corrected by the following formula:

Corrected output torque T2 (N.m) = theoretical output torque T1 (N.m) x working condition coefficient K


Working condition coefficient K value table


Prime mover Load condition Daily running time (hours)
0.5-2 2-6 6-10 10-24
Electric motor Smooth load 0.80 0.90 1.00 1.25
Medium shock 0.90 1.00 1.25 1.50
Big impact 1.00 1.25 1.50 1.75
Note: When the number of positive or negative reversals or stops is more than 10 times within 1 hour, the value of K in the above table should also be multiplied by 1.2.



2.Selection example


Transmission structure Related data
Lifting object weight   W=600kg
Lifting object speed   V=12m/min
Roller diameter       D=0.4m
Pulley transmission efficiency ƞ¹ =0.92
Reducer transmission efficiency ƞ² =0.71
Running time  8小时/日
Number of starts 2 times / hour, larger punch
Use power supply380V,50Hz



3.Selection step


Serial number Content Calculation formula Calculation example
1 Fixed gear ratio Determine the gear ratio based on the input and output shaft speeds
1, calculate the pulley speed n3
N3 = lifting speed V / (roller diameter Dx 71)
2, calculate the total gear ratio i
i=Input shaft speed Ni/pulley speed N3
3. Calculate the gear ratio of the reducer h
h=total gear ratio i/pulley transmission ratio b
1.N3=12/(0.4x3.142) = 9.6r/min
3. Set i2=5, then
2 Calculate the output torque Calculate the output torque of the reducer
T = object weight Wx10x roller radius (D / 2) / (pulley
Transmission transmission ratio i2 pulley transmission efficiency ƞ 1)
3 Corrected output torque According to the conditions of use, 8 hours of operation, large impact,
Working condition coefficient K=1.5 Calculate the corrected output torque T1
T2 = output torque TXK
=391 N.m
4 Calculate input power Conversion power P
P=corrected output torque Tx output shaft speed N2/ (9549x reducer transmission efficiency ƞ2)
5 Model specification According to the product sample, the selected model 120. Transmission ratio 1/30. Input shaft power 3kW. Output shaft torque 413N.m


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