Motor fixed end bearing
Fixed-end bearings use radial bearings capable of bearing combined (radial and axial) loads.These
bearings include: deep groove ball bearings, double row or paired
single row angular contact ball bearings, self-aligning ball bearings,
spherical roller bearings, combined tapered roller bearings, NUP type
cylindrical roller bearings or NJ type cylindrical roller bearings with
HJ Angle ring.
For the selection of motor bearing support fixed end (motor fixed end for short), the following factors should be considered:
(1) Accuracy control requirements of the dragged equipment;
(2) the load nature of motor drive;
(3) Bearings or bearing combinations must be able to withstand a certain axial force.
with the above three aspects of design elements, deep groove ball
bearings are more often used as the first choice for fixed end bearings
of small and medium-sized motors.
Deep groove ball bearings are the most commonly used rolling bearings.When deep groove ball bearings are used, the structure of motor bearing support system is very simple and easy to maintain.Deep
groove ball bearing is mainly used to bear radial load, but when the
radial clearance of the bearing is increased, it has the characteristics
of angular contact ball bearing and can bear radial and axial combined
load.When the speed is high and the thrust ball bearing is not suitable, it can also be used to bear pure axial load.Compared
with other types of bearings with the same specification and size as
deep groove ball bearings, this kind of bearings have the advantages of
small friction coefficient and high limit speed, and the disadvantages
are not impact resistant and not suitable for bearing heavy loads.
the deep groove ball bearing is mounted on the shaft, the radial fit in
the two directions of the shaft or housing can be limited within the
axial clearance range of the bearing.In
the radial direction, interference fit is used between bearing and
shaft, and small interference fit is used between bearing and end cover
bearing chamber or shell. The ultimate goal of choosing such fit is to
ensure that the working clearance of the bearing is zero or slightly
negative during the operation of the motor, so that the running
performance of the bearing is better.In
the axial direction, the axial match between the positioning bearing
and the associated parts should be determined in combination with the
specific situation of the floating end bearing system.The
bearing inner ring is limited by the bearing position limit step (shaft
shoulder) and the bearing retaining ring on the shaft, and the bearing
outer ring is controlled by the matching tolerance between the bearing
and the bearing chamber, the height of the inner and outer cover of the
bearing and the length of the bearing chamber.
Motor floating end bearing
The floating end of the motor is also called the free end, which is relative to the fixed end;In
general, the floating end is selected at the non-driving end, but in
the case that the motor load requirements are high, and the axial fit
size requirements with the load equipment are not very high, the
floating end will be selected at the driving end.
the motor bearing support system is double-fulcrum and double-bearing
structure, when the radial load requirements are large, the driving end
is also used as the floating end. Especially for low-voltage high-power
and high-voltage motors, the cylindrical roller bearings at the floating
end can meet the requirements of large radial load.
roller bearing roller and raceway for line contact or repair line
contact, radial bearing capacity is large, more suitable for bearing
heavy load and impact load, the inner or outer ring can be separated,
easy to install and disassemble.This
series of bearings have small friction coefficient and are suitable for
high speed and extreme speed close to deep groove ball bearings.Type
N and NU cylindrical roller bearings are commonly used in the motor.
The inner and outer rings of the bearings can be moved axially. They can
adapt to the change of the relative position between the shaft and the
shell caused by thermal expansion or installation error, and can be used
as free end support.However,
the bearing has higher processing requirements for shaft or bearing
chamber hole, and the relative deviation of inner and outer ring axis
after bearing installation should be strictly controlled to avoid
concentration of contact stress.
with the fixed end bearing, in order to meet the axial displacement
requirements of the rotor part during the operation of the motor, the
axial clearance requirements of the outer ring of the bearing and the
inner and outer cover of the bearing are different according to the
different bearing choices.
When the floating end adopts a bearing with separable inner and outer
rings, the fixed end is selected at the non-driving end for the
two-bearing structure motor;There
is no clearance between the outer ring of the fixed end and the
floating end bearing and the inner and outer cover of the bearing.
when the floating end of the non-detachable bearing, that is, small and
medium-sized motor are more common at both ends of the ball bearing
structure, in view of the impact on the installation accuracy of the
driving equipment, the driving end is the fixed end, the inner ring of
the floating end bearing should be limited, and the axial clearance
between the outer ring and the inner and outer cover of the bearing is
the same time, in order to ensure the axial fit displacement
requirements in the operation of the motor, the radial fit between the
outer ring of the bearing and the bearing chamber is not easy to be too
actual bearing configuration should be matched with the operating
conditions of the motor, including specific parameters such as
clearance, heat resistance, precision, and the radial matching
relationship between the bearing and the bearing chamber in the
selection of the motor bearing.