What are the technical parameters of motor shaft design?

The motor shaft is a cylindrical part protruding from the motor and its shell. The shaft is the main support and connection part of the armature part of the motor, and also the output part of the power generated by the motor. The purpose of the shaft is to convert the energy of the motor into the end use. The precision pin and motor shaft are used to improve the speed and torque of the power supply machine, and they are one of the indispensable important parts in the motor. Simple shafts are commonly used in motor applications, such as power steering control systems, small appliance motors, power tool motors and special components. Unreasonable design will lead to insufficient shaft radius, stress concentration caused by the change of installation position, which may lead to catastrophic failure of shaft after a short service life, so the shaft must meet certain technical requirements.

Strength and stiffness

When the motor is running, the form of mechanical force and torque on the shaft varies with the motor type and transmission mechanism. The main forces are: the gravity of the rotor assembly itself, the one-way magnetic pull caused by the rotor eccentricity, the centrifugal force of the unbalanced weight, and the load torque acting on the shaft by the transmission machinery at the shaft extension end. Therefore, the shaft of the motor should have enough strength to ensure that there is no residual deformation or damage in the working state and processing of the motor. At the same time, the shaft of the motor should have enough stiffness so that the shaft disturbance is within the allowable range when the shaft is working. The critical speed of the shaft should also be considered, and there should be enough difference between the working speed and the critical speed of the shaft, In order to prevent resonance, especially for the motor with high speed, the critical speed should be checked when necessary.

Surface hardness in the manufacturing process, the shaft often has to collide with the assembly mold. In the core punching, beer positioning ring and other processes, there is a certain amount of assembly interference. The hardness of the shaft must be higher than the positioning ring and chip material by a certain difference, so as to ensure that there is no shaft surface scratch, wound and other phenomena in the assembly. On the other hand, if the bearing is to be installed on the shaft, the surface hardness of the shaft must be controlled not higher than hv450. For rolling bearings, the surface hardness requirements of the shaft can be relaxed appropriately, and the surface heat treatment is generally not carried out.

Surface roughness

Surface roughness is a very important surface quality control parameter. If it is a sliding bearing, too high surface roughness will directly damage the oil film on the contact surface, thus increasing the wear of the bearing. But too low surface roughness will cause the friction between the shaft and the bearing molecules, which is also harmful. Therefore, we often control the scope of different materials and application conditions, the scope of control also changes accordingly. If it is a rolling bearing, when the surface roughness can not meet the requirements, the bearing section of the shaft will reduce the contact surface of the inner circle of the bearing, loosen the fit, and cause the bearing noise and noise. The shaft extension section will directly affect the connection accuracy with the load device, which is easy to cause vibration and noise. The iron core section will cause the change of air gap between stator and rotor and the flatness of chip arrangement, which will affect the performance of motor and the difficulty of chip winding.



Straightness (T.I.R.)



If the straightness of the whole shaft body does not meet the requirements, it will cause imbalance in the shaft core section and make the motor vibrate. In the bearing section, it will tilt the contact surface between the shaft and the bearing, resulting in the defective motor with low speed and high current. In the shaft extension section, it will make the connector vibrate and produce noise. In a word, the straightness of the shaft is a necessary condition for the normal operation of the motor. In the special environment, the material of the shaft is required to have certain corrosion resistance.



conclusion



In the manufacturing process of the shaft, the straightness of the shaft must be controlled to meet certain requirements, which comes from two aspects: one is the requirement of the transmission accuracy of the application device; the other is the requirement of the normal operation of the motor itself. The requirement of transmission accuracy of applied devices comes from the accuracy of applied devices, while the requirement of normal operation of motor itself is based on the comprehensive consideration of the clearance between shaft and bearing, vibration, noise and performance requirements of motor.