The clearance of a rolling bearing refers to the maximum distance that can be moved between the inner and outer rings of the bearing under no load, that is, when the bearing is not assembled on the shaft or the bearing box, the inner ring or the outer ring is fixed, and then The amount of movement when the unfixed side moves radially or axially. According to its moving direction, the radial movement is called the radial clearance, and the axial movement is the axial clearance.

  1. The radial clearance of the bearing will change correspondingly under different conditions, so it can be divided into original clearance, assembly clearance and working clearance:

  (1) The original clearance refers to the clearance in the free state after the bearing is assembled before being assembled in the machine and equipment. It is determined by the processing and assembly of the manufacturer.

  (2) The assembly clearance is also called the fit clearance, which is the clearance when the bearing and the shaft and the bearing seat are assembled but not yet working. Mainly because of the interference assembly, or the inner ring is enlarged, or the outer ring is reduced, or both, all make the assembly clearance smaller than the original clearance.

  (3) The working clearance is also called the effective clearance, which refers to the actual clearance in the bearing under the condition that the bearing is assembled in the main engine and realizes the stable operation of the corresponding temperature rise under the corresponding load effect. The working clearance is smaller than the original clearance, but compared with the assembly clearance, it is mainly because the inner ring has the largest temperature rise during operation and the largest thermal expansion, which reduces the bearing clearance. At the same time, it is mainly due to the effect of the load. , The elastic deformation caused by the contact between the rolling element and the raceway makes the bearing clearance increase. Whether the actual clearance is larger or smaller than the assembly clearance depends on the combined effect of these two factors.

  2. When the bearing clearance is too small, the bearing temperature is more likely to be too high. If the speed is faster, it may cause burnout. If it is operated in a high temperature and high speed environment for a long time, the bearing may be locked and cause damage to the supporting shaft of the bearing or the bearing position of the housing. When the bearing clearance is too large, the rotor will move during operation. Therefore, the size of the bearing clearance can directly interfere with the performance of the bearing's running accuracy, rotation flexibility, vibration, and noise. The clearance that does not meet the standard will cause the bearing to fail in the initial stage. Therefore, for the bearing used in vacuum transmission, the change of the clearance caused by the change of temperature and other factors must be considered in the whole process and the transfer in the solid lubrication bearing. Changes in clearance caused by membranes and trace wear debris.

  Three, the choice of clearance

  (1) The radial clearance of the ball bearing should be close to zero. The rigidity of the roller bearing is greater than that of the ball bearing. In order to avoid radial jamming due to the temperature difference between the inner and outer rings, the roller bearing should retain a certain radial clearance. For bearings that require rigidity or rotational accuracy, such as automotive wheel hub double-row angular contact ball bearings, a certain pre-tightening force must be applied to form a "negative clearance".

  (2) Light load, high speed, high precision, and low working temperature occasions

  Four. Measurement of clearance

  The bearing clearance is measured by a special clearance measuring instrument, and it can also be measured with a feeler gauge or a dial gauge.

  Check with a feeler gauge to verify the maximum load position of the rolling bearing. Insert the feeler gauge between the 180° rolling element and the outer (inner) ring. The thickness of the feeler gauge with suitable tightness is the bearing radial clearance. This specific method is commonly used in self-aligning bearings and cylindrical roller bearings; use a dial indicator to measure, first adjust the dial indicator to zero, and then jack up the outer ring of the rolling bearing. The reading of the dial indicator is the radial clearance of the bearing. .