Rolling noise analysis of NTN bearings

The rolling sound is due to the rolling of the rolling elements in the raceway when the NTN bearing rotates to excite a smooth and continuous noise, which only attracts attention when its sound pressure level or tone is extremely large. In fact, the sound energy excited by the raceway sound is limited. For example, under normal conditions, the quality of the 6203NTN bearing raceway is 25~27dB. This type of noise is the most typical of single row deep groove ball NTN bearings that can withstand radial loads. It has the following characteristics: a. noise and vibration are random; b. vibration frequency is above 1 kHz; c. no matter how the speed changes, noise master The frequency is almost constant and the sound pressure level increases with the increase of the rotational speed; d. When the radial clearance increases, the sound pressure level increases sharply; e. NTN bearing seat increases rigidity, the total sound pressure level is lower, even the rotational speed When the temperature rises, the total sound pressure level also increases little; f. The higher the viscosity of the lubricant, the lower the sound pressure level, but for grease lubrication, the viscosity and shape of the soap fiber can affect the noise value.

The rolling sound is caused by the natural vibration of the ferrule after the load. Due to the elastic contact of the ferrule and the rolling body, a nonlinear vibration system is formed. When the lubrication or machining accuracy is not high, the natural vibration associated with this elastic characteristic is excited, and when it is transmitted to the air, it becomes noise. It is well known that even with the most advanced manufacturing techniques used to process NTN bearing parts, there are always small geometric errors in the working surface, which causes small fluctuations between the raceway and the rolling elements to excite the natural vibration of the vibration system.

Although the rolling noise of the NTN bearing is unavoidable, in the high-precision machining of the working surface of the part, the NTN bearing is correctly selected and the NTN bearing is accurately used to reduce noise and vibration.

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Motor KOYO bearing cleaning process

The motor should normally be cleaned and refueled after 2000 hours of use. There are two cleaning methods for KOYO bearings:

1. Hot oil cleaning method Due to the long-term use, KOYO bearings hardened by soft dry oil or anti-rust paste should be immersed in hot oil of 100-200 °C, clamped KOYO bearing with pliers, and cleaned KOYO bearing with brush. Oil stains. The soft dry oil or rust-proof paste is melted when heated to 100-200 ° C, and is easily washed out from the gap of the KOYO bearing. Sometimes the KOYO bearing is shaken several times in the oil. Oil will also flow away from the gap.

When cleaning the centripetal spherical bearing of the old motor or the imported motor, the ball, the bead frame and the inner ring should be laterally turned out from the outer ring and then immersed in the hot oil. The short cylindrical roller bearing should also be rolled when cleaning. The bead frame, the inner ring and the outer ring are disengaged.

When hot oil is cleaned, the temperature of the oil should not exceed 20 °C. If you use an open flame to directly heat, you should take care to prevent the oil from burning. KOYO bearings should be hung in the oil pan, and the bottom will cause overheating and reduce the hardness.

Second, the general cleaning method put KOYO bearings in kerosene for 5-10 minutes, pinch the inner ring with one hand, and rotate the outer ring with the other hand, the dry oil or anti-rust cream on KOYO bearing will fall. Then put the KOYO bearing into the cleaner kerosene, brush it with a soft brush, wash the oil in the ball and the gap, then put it in the gasoline for 1 time, take it out and put it on a clean paper. When cleaning the radial spherical ball bearing and the short cylindrical roller bearing, the ball, the bead frame, the inner ring and the outer ring should be disconnected and cleaned.

The cleaning of KOYO bearings mounted on the shaft is mainly based on the method of spraying oil or spraying with oil guns. The oil that is easy to clean is first used with kerosene and then with gasoline; the oil that is difficult to clean is first washed with 100-200 °C hot oil. Wash or spray with oil and then wash with gasoline.

Be sure not to use a sharp tool to scrape the KOYO bearing: hard grease or rust, so as not to damage the smoothness of the KOYO bearing rolling element and groove ring. The cleaned KOYO bearing is wiped dry with a clean cloth.

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