The axial movement of motors is a problem that is difficult to avoid during the production and use of motors. Therefore, necessary measures must be taken during the design and production of motors to avoid the quality risks to the motor body or equipment caused by this.
For relatively small motors, ball bearings that can withstand a certain axial force can be used to solve the axial force effect when the motor is running; while for relatively heavy-loaded large motors, cylindrical roller bearings NU or N must be used at the shaft extension end. The inner and outer rings of cylindrical roller bearings have the characteristics of being separable, and cannot accurately control the movement of the rotor. In order to solve the problems of heavy load and axial movement of large motors, three-bearing structure motors have appeared.
Three-bearing structure motor, that is, one motor shares three sets of bearings. The non-shaft extension end uses a deep groove ball bearing, and the shaft extension end uses a set of deep groove ball bearings and a set of cylindrical roller bearings. The ball bearing at the shaft extension end plays an oil-directed positioning role. The bearing and the bearing seat are matched with a small clearance and do not bear radial loads. Light and narrow series deep groove ball bearings are mostly selected; the cylindrical roller bearing at this end plays a role in bearing radial force and is designed according to the matching relationship between the cylindrical roller bearing and the bearing chamber.
The cylindrical roller and the raceway are line contact bearings with large load capacity and mainly bear radial loads. The rolling element and the ferrule rib have low friction and are suitable for high-speed rotation. The inner ring or outer ring of the cylindrical roller bearing (NJ or N type) without ribs can move relative to each other in the axial direction. It is a bearing used as a free end. The cylindrical roller bearing with ribs on the inner ring (NJ type) or single ribs on the outer ring (NF type) can withstand a certain degree of axial load in one direction.
Single-row N and NU cylindrical roller bearings are widely used in motors. The outer ring of the N-type bearing has no flanges, and the inner ring has flanges on both sides. It can allow the shaft to move relative to the bearing seat in both axial directions. The NU-type bearing has flanges on both sides of the outer ring, and no flanges on the inner ring. It can also allow the shaft to move relative to the bearing seat in both axial directions. Therefore, this type of structure is suitable for use as a floating end bearing.
