When a pair of gears are machined, in the meshing process, the gear teeth will produce a certain degree of elastic deformation after being stressed. Therefore, whenever a gear tooth is meshed, the load of the originally meshed gear teeth will be relatively reduced, and they will immediately restore deformation towards the load position, so as to give the gear body a tangential acceleration. In addition, the bending deformation and gear manufacturing error of the original meshing teeth under load make the smooth contact of the theoretical tooth profile can not be obtained in the whole process from meshing in to meshing out, resulting in collision, forming the so-called meshing impact force.
Under this excitation, the gear will also arouse the circumferential vibration, radial vibration and axial vibration of the gear, so as to produce noise and spread it through air and solid media. Therefore, the wiring impact force and meshing impact force generated in the meshing process of gear processing make the vibration of a pair of transmission gears become the main cause of noise radiation.
When describing the mechanism of gear vibration and noise produced by gear machining, the gear can be regarded as a spring mass vibration system. The gear tooth is regarded as a spring and the gear is regarded as a mass. The pitch impact force and meshing impact force can be regarded as external forces, resulting in the circumferential vibration of the gear. Through the shaft system, the bearing induces the gear to produce radial and axial vibration. The vibration in these three directions is transmitted to the gearbox through the shaft, bearing and bearing seat, causing the vibration of the gearbox wall, and even inducing the vibration of the whole device, which radiates into the air and becomes the noise of the gearbox.
1. Forming method of gear machining: during milling, the workpiece is installed on the dividing head of the milling machine, and the disc (or finger) milling cutter with a certain module is used to mill the gear teeth. After machining one tooth space, carry out indexing, and then mill the next tooth space. Milling features: simple equipment, low tool cost and low productivity The accuracy of machining gears is low. The tooth profile shape of a gear depends on the size of the base circle (related to the number of teeth of the gear). The movement required for milling gears by forming method is simple and does not need a special machine tool, but it needs to be indexed by dividing head, which has low production efficiency. This method is generally used for single piece small batch production of low precision gears.
2. Generating method of gear machining: when using generating method to process gears, the involute on the gear surface is formed by generating method, which has high production efficiency and processing accuracy. The vast majority of gear machining machine tools use the generation method.