1. Design principle of gear induction coil
The size of the gear module plays an almost decisive role in the induction heating method and the structure of the induction coil. Of course, it is also related to the tooth width and the purpose of the gear. The gear module is large, which generally has higher requirements for the gear hardening layer. By consulting the relevant literature, there are generally three induction heating quenching methods for spur gears: Full Tooth quenching, single tooth quenching and quenching along the tooth groove. Their respective induction heating methods have their own heating characteristics. Each induction heating method generally has a corresponding coil structure. For example, the full tooth induction quenching method generally corresponds to the annular envelope induction coil, the single tooth quenching method corresponds to the tooth like induction coil, and the quenching along the tooth groove corresponds to the V-angle induction coil. However, there are induction coils that wrap the spur gear teeth with a tooth like structure.
The annular envelope inductor is generally only suitable for gears with modulus less than 5, but because all teeth are heated at the same time, the production efficiency is high. Single tooth quenching method refers to the induction heating method of completely covering the tooth top, which is suitable for simulating large gear parts. When induction heating, it is easy to overheat the tooth top, and there is no hardening layer in the tooth groove, which reduces the fatigue life of the gear. The quenching method along the tooth groove adopts an inductor similar to the shape of the tooth groove, which is suitable for continuous induction heating of single tooth of large module gear, and a more uniform hardening layer distributed along the tooth profile can be obtained. The three induction heating methods and corresponding inductor structures described above are all for spur gears, and there are few structural designs for bevel gear inductors.
2. Determination of bevel gear induction coil structure
The “disk-shaped” induction coil is designed in the early stage, and the coil structure is spirally distributed above the bevel gear, as shown in figure a). For the bevel gear, the induction heating analysis is carried out by using ANSYS software, and the frequency is adjusted. It is found that the tooth root can not reach the austenitizing temperature, mainly because the workpiece modulus of the bevel gear is 12, which is far greater than the required gear modulus 5. Later, it was considered to adopt profiling induction coil. When using integral induction heating, the induction coil structure is shown in Figure b). This coil structure is difficult to process and is not easy to process with copper pipe. In the induction heating experiment, the induction coil is required to have a continuous water cooling system to keep the induction coil temperature from being too high. If the moving induction heating method is used for induction heating, the profiling induction coil moves along the gear groove to conduct single induction heating on the tooth profile. However, because the bevel gear groove and teeth are inclined, the tooth shape and groove gradually become smaller from the big end to the small end, and the tooth width is generally large. When the quenching method along the groove is adopted, because the groove is inclined, the movement control angle is required to be higher when moving continuous induction heating, and because the size of the bevel gear groove gradually becomes smaller from the big end to the small end, and the structure of the induction coil remains unchanged, Therefore, not only the moving parameters are difficult to control, but also the induction heating effect along the tooth width direction is difficult to be consistent. Finally, the “tooth wound” induction coil as shown in Figure C) is designed to analyze the dual frequency induction heating process of bevel gear. This coil has simple structure and processing, is convenient for water cooling during the experiment, and can realize the austenitization of bevel gear tooth top and tooth root by adjusting the frequency.
