Due to the special structure of herringbone gears, its processing is more complicated than ordinary helical gears, and the equipment requirements are higher than those for helical gear processing. In terms of technical requirements, in addition to meeting the accuracy requirements of helical gears, there are also requirements for the position of the intersection point of the cogging extension lines of the left and right gears (hereinafter referred to as the center line of the herringbone gear). Usually the intersection point is on the center line of the two positioning end faces of the gear. This is also a difficult point in the processing of herringbone gears. Here are several common processing methods.

Soft tooth surface gear (the tooth surface hardness of the meshing gear pair is less than 350HB)

The more common processing methods for soft tooth surface gears include profiling and generative processing.

The profiling method refers to the use of a CNC machining center machine tool and a finger milling cutter for milling. The accuracy of this machining method is greatly affected by the tool, and the accuracy of the gear teeth is low, usually reaching the accuracy of about DIN8 , But the position of the center line of the herringbone gear is more accurate, and the overall processing efficiency is also low;

Generating method refers to the use of CNC gear hobbing machine for hobbing. Among them, if the gear hobbing machine control software has the herringbone gear processing function, the herringbone gear processing program can be used for processing. It is easier to ensure the center line position of the herringbone gear. The key is to process the gear. If the installation height of the herringbone gear is input accurately; if there is no herringbone gear processing function, it is necessary to mark the tooth surfaces of the left and right-handed gears before processing to determine the position of the center line of the herringbone gear, and then respectively The left and right gears are hobbed according to the scribing position. The center line position of the herringbone gear processed by this method is not easy to guarantee, and the accuracy of the scribing and the accuracy of the tool setting must be jointly determined; overall, the rolling is used The gear teeth produced by the cutting method have high precision (up to DIN7) and high processing efficiency;

Hardened gear

Hard surface gears are usually carburized or nitrided to the gear material, so that the surface hardness of the gear is about 60HRC. If the gear is nitrided, the teeth must be made live before heat treatment. The processing method is the same as that of soft teeth. Face gears are the same; if the gear is carburized, the teeth must be made alive after heat treatment. The processing method is usually gear grinding. The center line of herringbone gear can be adjusted during gear grinding. Due to the limited amount of hobbing, Therefore, the adjustment amount of the center line of the herringbone tooth is limited, and the position of the center line of the herringbone tooth is determined by the machining accuracy before heat, but the precision of the gear processed by grinding can reach DIN5 or higher.

Concluding remarks

Since the herringbone gear has the characteristics of automatically offsetting the axial force, increasing the helix angle has no effect on the force of the entire transmission system, but on the other hand, a larger helix angle can get a larger coincidence degree, making the transmission more stable . The gearbox with herringbone gear pair has the remarkable characteristics of stable transmission, low noise, small size, light weight, large transmission power and long service life, and has high comprehensive social benefits. It can be seen that the herringbone gear transmission is an important development direction of the gear transmission mechanism, and we need to further improve the existing manufacturing level.