The two main factors that traditionally measure gearing performance are load capacity and fatigue life, which often ignore transmission noise and transmission accuracy. As the ISO14000 and ISO18000 successively promulgated two standards, control gear transmission noise the importance of this factor has become increasingly obvious, industrial development and the demand to the requirement of high precision equipment transmission error is becoming more and more strict (gear side clearance). At present, the known gear noise forming factors can be analyzed in terms of design, manufacture, installation and maintenance.
Design reasons and countermeasures
1. Gear accuracy grade
Gear drive system design, the designers often from economic factors to consider, as far as possible the determination of economical gear precision grade, but precision level is gear noise level and the lateral clearance of tags. The United States gear manufacturing association has used a large number of gear studies to determine that the high-precision grade gear produces less noise than the low-precision grade gear. Therefore, it is necessary to improve the precision grade of gear to reduce gear noise and reduce transmission error.
2. Gear width
When the gear drive system is allowed, increase the width of the teeth and reduce the unit load under constant torque. Reduce the noise excitation and reduce the noise. The study of H o 'paz in Germany showed that, when torque was constant, the width of small teeth was higher than that of big teeth. At the same time the increase of tooth width can increase the bearing capacity of the gear.
3. Tooth distance and pressure Angle
The small pitch can ensure that there is more gear tooth contact, the gear overlap increases, reduces the individual gear deflection, reduces the transmission noise, improves the transmission precision. The smaller pressure Angle is larger because the gear contact Angle and the lateral overlap ratio are larger, so the running noise is small and the accuracy is high.
4. Speed of operation
According to the experimental study of H orpaz in Germany, the noise level increases with the increase of gear speed.
5. Gear box structure
The experimental results show that the cylindrical box is advantageous to the shock absorption, and the noise level of the normal structure gearbox is 6dB higher than that of the cylindrical box in the same condition. The resonant position of the gear box was found, and the resonant position was found, and the appropriate reinforcement bar (plate) was added, which can obviously reduce the vibration and reduce the noise. The multistage gear transmission requires that the instantaneous transmission ratio change as small as possible. It has ensured that the transmission is stable, the impact and vibration are small and the noise is low.
6. Analysis of gear acoustic radiation characteristics
In the selection of gears with different structural forms, the acoustic radiation model is established for the specific structure, dynamic analysis is carried out, and the noise of the gear transmission system is pre-evaluated. For according to the different requirements of users (whether use place, unmanned, whether within the urban area, the ground, underground buildings have specific requirements, if there is a noise protection, or other specific requirements) to meet.
Manufacturing reasons and countermeasures
1. Error effects
Tooth profile error, pitch error and tooth alignment error of manufacturing process are the main errors of driving noise. It is also a problem point that the gear transmission accuracy is not guaranteed.
The gear with small tooth shape error and small tooth surface roughness is 10dB smaller than normal gear under the same test condition. In the same test condition, the noise level is 6 ~ 12dB smaller than the normal gear. But if there is an error in the pitch, the load will have less impact on the noise of the gear.
The tooth alignment error will cause the transmission power not to be transmitted through the whole tooth width, and the contact area will turn to the end face or the end face, which increases the noise level by increasing the deflection of the tooth. But in high load, the tooth deformation can partially offset the tooth error.
The production of gear noise is directly related to the transmission precision.
2. Assemble the concentricity and dynamic balance
Assembling different heart will lead to unbalanced operation of shafting, and because the tooth theory meshes the half of the half of the loose half, the joint causes the noise to increase. The unbalance of high precision gear assembly will seriously affect the precision of transmission system.
3. Hardness of tooth surface
With the development of gear tooth surface technology, its carrying capacity is large, small size, light weight and high transmission precision. But in order to obtain the carburizing hardening of the hardened teeth, the gears can be deformed, resulting in the increase of the gear transmission noise and the shortening of life span. In order to reduce the noise, the tooth surface should be processed. Besides the traditional grinding method at present, and to develop a method of hard tooth face scraping by modified tooth top and tooth root, or the main drive gear tooth profile are small, to reduce the gritting gear meshes into and out of shock, thus reducing gear noise.
4. System index verification
On machining precision of parts before assembly and parts matching method (completely interchangeable, group matching, single matching, etc.), will affect the precision of the system after the assembly level, their level of noise is in the range of influence, therefore, after the assembly of the indicators system for verification or calibration, noise is key to control system.