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Practical inspection of EV Vacuum Pump gears

Pulished on Jan. 16, 2020

Gear processing and inspection require special equipment. In order to reduce costs and improve production efficiency, the Electric Vacuum Pump Kit Factory usually adopts the form of external processing, but these and other problems often occur in the use of these gears, so inspection is very important. 
The problem caused by gear deviation is mainly the abnormal contact during operation, which will inevitably produce abnormal noise, so it can be solved by noise measurement and analysis. Different problems generate noise at different frequencies and the cause of noise can be analyzed to solve it through noise spectrum analysis. The fundamental frequency of gear noise is:

EV Vacuum Pump

EV Vacuum Pump

a, tooth profile deviation
The abnormal meshing caused by tooth profile deviation will produce different levels of noise depending on the degree of deviation. Its noise frequency can be calculated according to formula. This situation is generally not suitable for rework, because of re-positioning installation is easy to produce new positioning deviation. If the situation is not very serious, you can take a very fine layer of corundum on the tooth shape and perform rotary grinding to obtain good results.
b, the gear clearance is too small
The reasons for the small gap between the two gears are: the tooth the profile is too fat during gear processing or the center distance of the bearing hole is too small during the processing of the two side covers, which will cause the gear center distance to be too small, which will make it in operation The gears are severely squeezed, hot, and emit continuous high-frequency noise.
Noise abnormality (high) can be found at the gear noise fundamental frequency on the noise spectrum and abnormal squeeze marks can be found on the surface of the gear during disassembly. If it is not replaced in time, the gear continues to heat up and expand, which will cause a seizure.
c, the gear gap is too large
The reasons for the excessively large gaps between the gears are: the tooth profile is too thin during gear processing or the center distance of the gears are too large due to the large center distance of the bearing holes on both sides of the cover, which makes it difficult to adjust the gap between the rotors, or even Cannot be adjusted
It is more obvious than during the stoppage of the pump, the rotational inertia of the driving rotor (with the motor) and the driven rotor are different, resulting in an inconsistency in the reduction of the rotation speed during the stoppage, resulting in a difference between the driving rotor and the driven rotor. An impact is generated, and the noise emitted by the impact is very loud, and its frequency decreases with the decrease of the rotation speed, and it can be quickly distinguished only by the sense of the ear.
This kind of noise, which does not occur during normal operation, but only during the process of stopping rotation, is a characteristic of noise caused by excessive gear clearance. When this happens, the gear must be replaced. Maybe the fat and thin gears are paired and checked. Maybe they can be used.
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