Role and characteristics of couplings

Couplings are mechanical parts used to connect two shafts (main shaft and driven shaft) in different organizations so that they rotate together to transmit torque. The coupling consists of two halves, which are coupled to the main shaft and the driven shaft respectively. Most of the general power machine with the help of the coupling and the working machine connected.

Role and characteristics

1. Transmit torque. When the torque exceeds the limit, it can also play the role of overload protection through its own destructive effect.

2. Due to its own structural characteristics, with a certain degree of flexibility, thus allowing a small amount of drive shaft eccentricity, deflection and other installation errors, and can absorb a certain axial amplitude.

3. Non-metallic elastic intermediate, but also has a certain degree of electrical insulation.

4. In the high-speed heavy-duty power transmission, some couplings also buffer, vibration damping and improve the dynamic performance of the shaft system.

Rated torque (N-m) and maximum torque (N-m)

1. Rated torque is the value that ensures that fatigue damage to the coupling does not occur when the shaft is twisted. Maximum torque is the maximum torque value that can be transmitted instantaneously by the coupling.

2. When the motor is started, stopped, or switched forward and backward, a higher torque may be generated than when the motor is in normal operation.

3. Make sure that the normal operating torque does not exceed the “rated torque” and that the instantaneous torque does not exceed the “maximum torque”. When switching frequently between forward and reverse, make sure that the coupling “rated torque” is 2 to 5 times higher than the maximum torque of the motor. When switching frequently between forward and reverse, please make sure the “rated torque” of the coupling is higher than the maximum torque of the motor by 2~5 times.

4. When using servo motors, please make sure that the “rated torque” of the coupling is 5~10 times higher than the maximum torque of the motor.

Maximum speed (rpm)

The maximum speed that can be used. The design ensures that the maximum speed of operation is below the “maximum speed”, and dynamic balancing may be required for use at high speeds.

Moment of Inertia (kg-meter)

Indicates the size of the rotational inertia of the coupling. The smaller the moment of inertia, the smaller the load torque that the coupling is subjected to at the moment of starting and stopping.

Static torsional rigidity (N-m/rad)

The torsional rigidity of a coupling. Indicates the difference in response between the input shaft and the output shaft in the direction of rotation when a torque is applied to the coupling. The higher the static torsional rigidity, the better the response of the coupling to the servo system and the higher the control accuracy.

Allowable Deviation

1. Radial deviation (mm): the permissible value of the parallel deviation of the two coupling axes.

2. Angular deviation (°): the permissible value of the angle between the center lines of the two coupling shafts.

3. Axial deviation (mm): the permissible value of axial reciprocating movement of the two coupling shafts.

4. If the mounting exceeds the allowable values, vibration may occur or the life of the coupling may be shortened, so be sure to calibrate the “radial misalignment,” “angular misalignment (°),” and “axial misalignment (mm)” so that they are below the allowable values listed in the specification sheets for each product. The “Radial Deviation”, “Angular Deviation (°)”, and “Axial Deviation (mm)” are calibrated to be lower than the allowable values listed in the specification sheet of each product.

5. The maximum tolerance value of deviation listed in each product refers to the situation where one deviation exists. When two or more deviations exist at the same time, the tolerance value should be less than 1/2 of the maximum deviation listed in the specification table.

6. Deviations do not only occur in the assembly of the equipment, but can also be caused by vibration, thermal expansion, bearing wear, etc. during operation. Therefore, it is recommended to adjust the axial deviation to less than 1/3 of the maximum value.