what are the common types of motor shafts

Shaft is an important part of motor, which is used as the link of electromechanical energy conversion between motor and equipment to support rotating parts, transfer torque and determine the relative position of rotating parts to stator. Therefore, the motor shaft must have reliable strength and stiffness to ensure the realization of pre-set design function. The following Ms. Reference briefly describes each type of motor shaft and its characteristics to provide reference for the selection and design of motor shaft.

Types of axes and their applicability

● classification according to whether there is a ladder on the axis. It can be divided into optical axis and stepped axis. The optical shaft is usually made of cold-drawn round steel, which can reduce the working time of machining the shaft's outer circle. It is sometimes used in micro motors. Stepped shafts are convenient and reliable for mounting many different parts, so most motors use them.

In the stepped shaft, according to the different direction of the step, it can be divided into one-way step shaft (the diameter of the step decreases from one end of the shaft to the other end) and two-way step shaft (the diameter of the step decreases from the middle of the shaft to both ends).

● according to the axis billet manufacturing method classification. It can be divided into a round steel shaft (made of a hot rolled round steel car), a forging shaft (made of a forging piece), and a welding shaft (welded with radial bars).

The shaft made of hot rolled round steel is the most common shaft in small and medium-sized motors. The shaft is usually made of 45 high quality carbon structural steel. For small power motor, some use Q235 ordinary carbon steel. The blank diameter should be selected according to the maximum diameter of the shaft plus the machining allowance. Therefore, the cutting quantity is relatively large.

The shaft with diameter above 100 mm should be forged shaft. The forged steel has high mechanical strength and the rough shape of the stepped shaft can save raw materials and cutting time. For large shafts with high mechanical strength requirements, such as those for turbo-generators, alloy steel is often used for forging.

By replacing the rotor bracket with radial bars, the ventilation area of the rotor cavity can be increased. However, when welding the bar, it is easy to cause the deformation of the shaft. In the machine tool processing and discontinuous cutting, adverse to the tool. Due to the existence of welding seam, the fatigue strength of shaft is significantly reduced, so it is not suitable for high-speed motor.

● according to the combination of shaft and core. It can be divided into middle knurled shaft, hot set shaft and middle shaft with keyway. Knurling shaft is used for small motor under 10 kw, which can save the work of machining key seat and key seat. However, when the shaft is pressed into the core, it is easy to deform the shaft. In the motor operation, some knurled rotor core produces the phenomenon of axial movement. The axial deformation is caused by the fit between the core and the shaft, and the axial displacement is caused by the fit between the two.

The middle portion of the sleeve shaft is neither knurled nor keyway. A certain amount of interference is left between the shaft and the inner hole of the core. The combination of rotor core and shaft is very reliable as long as the interference amount is selected properly.

The shaft with keyway in the middle can be divided into one section of keyway and two sections of keyway. The shaft with one section of keyway is used for small motor. Shafts with two keyways are used for medium and large motors. The rotor core (or bracket) is bonded to the shaft. The iron core is fixed in the axial direction. One end is added with a convex shoulder, and the other end is stuck in the annular keyway of the shaft with an arc key. This shaft can transfer greater torque, and is often used for larger power motor and the operation of frequent positive and negative rotation or rotor core should not be hot jacket motor.

● according to the axial extension shape classification. Can be divided into cylindrical shaft extension, conical shaft extension and shaft extension with half coupling shaft. Cylindrical shaft extension processing is convenient, most used in motor. Circular d shaft auxiliary extension with fastening bolts, processing quantity is large. However, the equipped driving wheel is convenient for loading and unloading, and is often used for special motors. The shaft with half coupling is mainly used in hydraulic generator and large direct current machine.

● classification by axial shape. It can be divided into solid shaft, shaft with deep hole at one end and shaft with center through hole. Solid shafts are most commonly used in motors. The shaft with a deep hole at one end is mainly used for winding asynchronous motors to connect the lead wire on the rotor through the hole and the collector ring outside the end cover. Shafts with central through-holes are mainly used for large motors: in turbo-generators cooled in double water, the central through-holes are also used as part of the cooling waterways.

● classification by axial magnetic conductivity. It can be divided into permeability axis and non-permeability axis. Magnetic conductivity shaft is mainly used in turbine generator. Other motors usually have shafts that do not require magnetic conductivity.

● other classification methods. According to the different number of shaft extension, it can be divided into single shaft extension and double shaft extension. According to the number of bearings, it can be divided into single bearing shaft, double bearing shaft and multiple bearing shaft.