Analysis on the application of UD planetary disc reducer
——Ningbo Zhenhai reducer manufacturing Co., Ltd Zhan Longhai, Huang Jiping
preface:
Due to its structure and working characteristics, the corresponding driving mechanism has some basic requirements: large starting torque, strong overload protection, simple flow regulation, good corrosion resistance, and rotation speed N2 ≤ 800r / min. At present, the common driving sources are: multi pole (such as six pole and eight pole) motor direct drive; motor + reducer deceleration drive; frequency conversion variable deceleration drive composed of frequency converter + motor + reducer; electromagnetic variable deceleration drive composed of electromagnetic speed regulation + motor + reducer; mechanical variable deceleration drive composed of motor + UD planetary cone reducer. The screw pump manufacturer has made various driving configurations according to different working conditions and user requirements, and has obtained different experiences and gains. UD planetary cone plate reducer is used in single screw pump. Because of the lack of knowledge of various factors, the author makes an analysis of the driving according to the advantages and disadvantages of the application results over the years.
1： Mechanical characteristics and working principle of UD planetary reducer:
UD planetary cone plate reducer (DISCO CVT) is a planetary traction CVT type. The following is the mechanical characteristics and working principle of the product:
1. Mechanical properties:
1) M-n2 characteristic curve:
2) Slip rate
ε: Slip rate: it indicates that there is a certain slip between the actual output speed and the theoretical output speed of the transmission in operation.
ε=（1-n2/n02）×100%
N2: actual output speed N02: theoretical output speed
The slip rate of UD planetary bevel reducer is less than or equal to 10% in normal operation
3) Gear ratio RB
RB: indicates the transmission capacity
Rb=n2max/n2min
N2max: maximum output speed n2min: minimum output speed
RB ≤ 5 in normal operation of UD planetary bevel reducer
2. Working principle:
The power source drives the sun gear by the motor input, and drives the planetary gear to move through the traction fluid (lubricating oil). The planetary gear rotates and rotates at the same time, and drives the rotating arm and output shaft to run through the sliding block bearing to output power. Through the speed regulating device, the contact radius between the sun gear and the planetary gear is changed to realize stepless speed change. Under normal working conditions, there is a layer of oil film between the friction drives, and the power is transmitted according to the route of driving part → oil film → driven part (so-called traction drive).
2、 UD planetary cone disc reducer features single screw pump application:
one Large starting torque: when the single screw pump starts, the load torque is often very large in a short time, while the UD planetary bevel reducer drive can withstand overload work, only the slip rate ε increases rapidly and the speed drops obviously, but when the external load is normal, the slip rate returns to the normal value ε ≤ 10%, and the pump speed also tends to work normally, even if the start is frequent, the impact is not serious The life of the sound reducer. At the same time, according to the mechanical characteristic curve, the constant power characteristic can be used to start in the middle speed section. At this time, the output torque can be used to overcome the overload condition of single screw pump.
two Adapt to flow change conditions: when single screw pump is working, due to the change of working conditions or the wear of pump parts, the flow of the pump needs to be adjusted. At this time, the ideal flow can be obtained by turning the transmission hand wheel, changing the contact radius between the sun gear and the planetary gear, and changing the output speed. The speed regulating mechanism is a simple mechanical mechanism, which will not be affected by the bad working conditions of the screw pump Because of the influence of environment (humidity, pollution, etc.), it is easy for operators to master and use it.
three The particularity of motion ensures the reliability of the product: according to its working principle, UD planetary bevel reducer drive is not a simple mechanical transmission, but a special traction (oil) transmission, so it has a great relationship with the traction coefficient μ of the oil. The special oil for ub-3 transmission developed by Guangzhou Institute of Mechanical Research Co., Ltd. has the traction coefficient μ = 0, 09 ~ 0, 074, and all transmission systems are stable The moving parts of the actuator work in the environment full of oil instead of the direct contact of the mechanical moving parts. Its main moving parts are well lubricated and protected.
4. Good overload protection performance: when the screw pump stalls, because the sun gear on the motor output shaft is not directly rigidly connected with the intermediate rolling element planetary gear, but through the flexible connection of the traction fluid, when the screw pump stalls, the traction force of the oil is not enough to drive the planetary gear to rotate, resulting in slippage, In a short period of time, the motor is still running at a constant speed, the motor will not be greatly impacted by the current, so that the motor can be guaranteed, and the service life of the motor is longer.
5. Improve the equipment utilization rate of the pump set: UD planetary cone reducer changes speed, the speed ratio RB is generally 5, when the speed N2 changes downward, the output torque M also increases, when the load becomes larger, properly slow down the speed, the screw pump can still work normally. Or when the stator and rotor wear is large and the volumetric efficiency is low, properly increasing the speed N2 can keep the flow stable, which can improve the equipment utilization of the pump set.
6. Improve the equipment economy of the pump set: the combination of UD planetary cone reducer and single screw pump is optimized as a whole, the reducer is equipped with thrust bearing to bear the axial thrust generated by the screw pump, and the pump omits the bearing seat; the output structure of the reducer is connected with the screw pump by adopting the short hole scheme, and the coupling structure is omitted, so as to simplify the assembly process and improve the alignment. After the structure optimization of the pump set, not only the cost is reduced, but also the working accuracy of the pump set is improved.
3： Problems in the application of single screw pump in UD planetary bevel reducer
1. Problems of design and selection
Case: a project in Shandong purchased a batch of UD planetary cone reducer driven single screw pumps
Design requirements: conveying medium: Industrial biochemical sludge, q = 2 ~ 12 m3 / h
Design selection: udy7.5-100
Model Description: UD planetary transmission (basic type, without reducer), motor power: P = 7.5kW, four pole, output speed n = 100-500r / min, horizontal coupling connection structure
Problem: after the project is delivered, the actual required flow rate is 2 ~ 3 m3 / h, and the pump working point speed is 100 R / min
After using for 2-3 months, the transmission found noise. Soon after it was still in use, the transmission failed. When the motor rotates, the output part does not rotate. The user thinks that the product is defective and complains.
Analysis: according to the m-n2 characteristic curve, the efficiency η is the minimum, the slip rate ε is the maximum, the wear is serious, and the service life is very short.
Cause: during the selection, the parameters are not accurate and the performance of the transmission is unknown.
Countermeasures: after negotiation with the user, reduce the power, adopt P = 5.5kW, six pole motor, reduce the output speed of the transmission, and shift the working point to the right. After the motor was replaced, the pump unit worked normally for several years.
2. Problems of management and use
Case: a water treatment company in Zhejiang imported water treatment equipment. After 2-3 years of operation, it was found that a number of pump sets, such as filter press and dosing pump, were continuously damaged. The failure to contact the importer seriously affected the operation of the water treatment project. The users have serious doubts about the quality of foreign products.
Analysis: through the field test of domestic transmission professional manufacturers, many driving sources are planetary bevel reducer. The cause of the accident is unknown to this type of product, which is not suitable for management. Lack of oil or filling high viscosity oil leads to transmission failure.
Causes: unclear structure, improper use and management.
Countermeasures: quickly change the special oil for speed change, check the working point, and adjust the speed according to the requirements of working conditions. The flow tends to meet the requirements. The product has been under normal management and use, and the equipment has operated normally for many years.
Conclusion:
UD planetary cone reducer applies single screw pump. Based on the analysis of the practical application results for many years, due to the special performance of the product, it can make the pump set play its equipment value well, but at the same time, it requires clear understanding of the structure and performance of the product and correct management, otherwise it is easy to cause problems and damage to the product. Therefore, the promotion and application of this project must have the preliminary work of professional knowledge popularization, otherwise, it is easy to fall short and backfire. The author analyzes the advantages and disadvantages of UD planetary cone reducer as the driving source of single screw pump for reference.
