Reducing motor bearing noise requires control across multiple stages-including design, manufacturing, lubrication, and installation. Key measures include designing bearing rib coefficients according to national standards; preventing impacts and maintaining cleanliness during manufacturing; selecting low-noise greases (such as Kyodo Yushi products); ensuring the inner ring is pressed onto the rotor while the outer ring maintains a loose fit; and applying appropriate preload via wave washers while avoiding direct hammering. Abnormal bearing noises primarily include cage noise, continuous humming, "paint rust" (corrosion caused by varnish fumes), noise from contaminants, and high-frequency vibration. Cage noise can be mitigated by selecting bearings with small internal clearance, applying preload, reducing moment loads, minimizing installation errors, and using high-quality grease. Solutions for continuous humming include using grease with excellent lubricating properties, applying preload, minimizing installation errors, selecting bearings with small radial clearance, increasing housing rigidity, and enhancing self-aligning capabilities (e.g., using a 02-series groove curvature). Paint rust can be prevented by air-drying or baking the rotor and housing before assembly, lowering motor operating temperatures, selecting varnish-compatible bearing models, improving storage conditions, using suitable grease, and employing vacuum varnish impregnation processes. Noise from contaminants can be addressed by using high-quality grease, ensuring cleanliness prior to greasing, enhancing seal performance, and maintaining a clean installation environment. High-frequency vibration can be reduced by improving raceway surface finish (to lower waviness amplitude), minimizing surface damage, optimizing clearance/preload/fits, checking the operation of the free-end bearing, and improving installation precision and methods.
Causes of excessive bearing temperature rise include incorrect grease type or quantity, insufficient internal clearance, installation errors, friction from sealing components, and bearing creep. Solutions involve selecting the correct grease and controlling the dosage; adjusting clearance, preload, and fits while checking free-end bearing operation; improving housing precision and installation methods; and optimizing seal designs.
The internal clearance of a bearing during operation should be a very small positive value. The selection method involves taking the initial clearance and subtracting the reduction caused by tolerance fits and the change caused by temperature fluctuations to ensure the operating clearance suits the working conditions; for industrial motors, C3 clearance is generally recommended (except for small motors). When determining tolerances and fits, the material's thermal expansion coefficient must be considered; for instance, fits for aluminum-casing motors should be one grade tighter than those for cast-iron frames. Generally, rotating components require tighter fits, while stationary components allow for looser fits; however, if the bearing's outer ring rotates, the outer ring fit should be tight while the inner ring fit can be loose. Grooving the bearing housing to accommodate an O-ring can prevent outer ring creep caused by thermal expansion in aluminum-casing motors.
Regarding material and structural selection, engineering plastic cages are lightweight and suitable for high-speed applications or scenarios where sudden shutdowns are impermissible, with a typical temperature range of -40°C to 120°C; brass cages are unsuitable for ammonia-rich environments, whereas steel cages have no specific limitations. In terms of sealing, dust shields offer protection against dust but provide no actual sealing function, maintaining speed performance comparable to open bearings; rubber seals provide effective sealing but reduce speed capabilities, with standard rubber rated for approximately 120°C and high-temperature fluororubber for around 180°C.
Regarding installation and maintenance, vibration motors require tight fits for both the shaft and the bearing housing; grease containing EP (extreme pressure) additives should be used, and lubrication intervals should be shortened. Bearing failures primarily manifest as overheating and abnormal noises: distinct rolling vibration sounds indicate excessive internal clearance; a dull, muffled sound suggests lubricant contamination; irregular knocking sounds indicate a fractured or dislodged rolling element; and a whistling shriek accompanied by rolling sounds indicates severe lubricant starvation. For applications demanding high speeds, high precision, low noise and vibration, high temperatures, or stringent sealing and lubrication standards-such as drive motors for new energy vehicles-a comprehensive evaluation of bearing dimensions, cage type, lubrication method, internal clearance, and seal type is required.
