What Is a Drive Shaft?
A drive shaft is a mechanical element that transmits power from an actuator, such as a motor, to a driven shaft via a transmission mechanical element.
Transmission elements include gears, timing belts, V-belts, and chains. Drive shafts must be able to rotate with high precision under high loads.
Therefore, they must be stronger and more precise than driven shafts. Drive shafts also require keys and other fastening mechanical elements to connect with the transmission mechanical elements.
Applications of Drive Shafts
Drive shafts are used in a wide variety of industrial machinery. Examples include construction machinery, machine tools, and various types of manufacturing equipment. Drive shafts are used in machines powered by motors to transmit the rotation generated by the motors.
Drive shafts are designed and manufactured arbitrarily according to the environment and machine system in which they are used. However, drive shafts of frequently used shapes are standardized and lined up as products by various FA equipment parts manufacturers.
Principle of Drive Shafts
Drive shafts are usually supported by bearings to ensure rotational accuracy. The bearing must support the rotating shaft of the drive shaft so that it does not shake while receiving the torque that the shaft is subjected to. The shaft part is generally manufactured with h6 or h7 tolerance.
Drive shafts must be strong enough to withstand high torsional torque and wear resistance. Heat treatment, such as high-frequency quenching, is required for this purpose. Here, carbon steel for machine structural use such as S45C is used, and the surface hardness is quenched to HRC50 or higher.
To improve corrosion resistance, surface treatments such as iron tetroxide coating or electroless nickel plating are applied. For food or clean environments, SUSU304 is used.
Other Information on Drive Shaft
1. Drive Shafts and Driven Shafts
A driven shaft is a shaft that is driven by power transmitted from the drive shaft through mechanical elements such as gears and joints. The driven shaft is the output side, while the drive shaft is the input side, and is set to output the values intended by the designer, such as rotational speed and torque. Therefore, the power transmission mechanism must be selected after calculating the reduction ratio and rotation speed.
The drive shaft is an input shaft to obtain some output and is always used in combination with a driven shaft. If there is no driven shaft, the name drive shaft is not used because the input shaft is not used to obtain an output. A drive shaft is the name used for the shaft that inputs power. However, any shaft that is moved by power transmitted from the drive shaft is called a driven shaft. Therefore, shafts other than the final output shaft may also be called driven shafts, and propulsion shafts and transmission shafts are categorized as driven shafts.
2. Design of Drive Shafts
To design a drive shaft, it is first necessary to determine the magnitude of the input power and the desired output power. The input power is determined by the device used for power, such as an engine or motor, and the reduction ratio and rotational speed are calculated to obtain the output value.
Based on the calculated rotational speed and torque, a material is selected that is strong enough to withstand the load that the drive shaft is subjected to. The most important loads to which the shaft is subjected include rotational moment, torsional load, impact, and frictional force, but the most important are static strength and fatigue strength due to shaft torsion.
Since drive shafts are used in combination with bearings, not only the shaft material but also the diameter and length of the shaft are important. If the diameter of the shaft is too thin, it will not be able to support the torsional load sufficiently, resulting in a rupture. If the length of the shaft is too long, it will be affected by bending moments, leading to shaft deformation. The point where the shaft is supported by the bearing is also important. The distance from the bearing to the end of the shaft should be as short as possible to maintain the strength of the rotating shaft.