Research On The Loading Capacity Of Cylindrical Helical Gear Affected By Machining Errors

Helical gears as an important component parts of the transmission, which were widely applied in mechanical transmission with the excellent mesh performance and high load capacity. In the gear machining process, it was believed that machining error generated affected by the processing principle and technology systems. While the existence of machining error exacerbated tooth surface localized pitting corrosion, wear and premature failure of gear, which there was an obvious impact on the service life and the loading capacity for continuous engaged helical gear drives. Therefore, in order to improve the service performance and service life of the mechanical transmission, a quantitative investigation was performed for the effects of machining error on the loading capacity for continuous engaged helical gear drives. The main contents were as follows:The profile error and helix error on the tooth surface were measured on the gear measuring instrument. On the basis of the test data, the distribution rule of tooth machining error was obtained using the knowledge of mathematical statistics, which provided useful guidelines for the derivation of the equations of tooth surface with machining error.The quantitative mapping rule research between rack-cutter machining errors and the tooth machining errors with the consideration of machine tool movement error were carried out respectively based on the conjugated theory and given rack-cutter equation. Thus, the equations of tooth surface with helix deviation and profile deviation were established. It was great important to provide a theoretical basis for building the gear geometry model and finite element model(FEM).According to the equations of tooth surface with machining error, the gear geometry model and finite element model with the consideration of machining error were established using the technology of surface reconstruction under the environment of ANSYS_APDL. The characteristic of the error modling method was that it could directly introduce to the machining error of gear and adapt to the type of the machining error variation of the helical gear rapidly in ANSYS. And the results were compared to the modling method using UG software as specified by the fifth model and full model. It was found that the relative error of the two modeling method were all controlled within 5%. The accuracy of gear contact analysis by FEM and the feasibility of modeling method proposed in this paper were verified.Based on those error(profile deviation, helix deviation and pitch deviation) FEM models, the effect of single tooth deviation including pitch error, profile form error,profile slope error,helix form error and helix slope error on the tooth contact stress(TCS), tooth surface load distribution(TSLD), tooth root bending stress(TRBS) and transmission error(TE) were investigated and the results were compared to each other as specified by grades 5 and 7. The results showed that the single tooth deviation not only reduced the contact strength and bending strength, but also changed the TSLD distributions. There was little effect of load distribution affected by profile slope deviation and helix slope deviation while it was affected by profile form deviation, helix form deviation and pitch error. Meanwhile, the effects of HFD on the loading capacity for continuous engaged helical gear drives depended on shape, amplitude and period of HFD. And the results also showed that the HFE and TFE mainly affected the TSLD and TRBS along axial direction, and would exert severe overloading. The maximum TSLD, TCS and TRBS increase nearly doubles when the grade changed from 5 to 7, where the value of machining error were doubled. The effects of HSD and TSD on TSLD, TCS and TRBS would exert the sharp soar of local load at the root or addendum.Finally, Based on the combination model with machining error, this subject analyzed the influence of the combination of different types of machining errors on the tooth contact stress. The results showed that the machining errors had a cumulative effect on the contact stress, which was great larger than that the single TSE and HSE combinations. Thus, the combination of different types of machining errors could exacerbate the service life of gear.The proposed modeling method with machining errors provided an effective way to analyze the real situation of the loading capacity of helical gear. Moreover, this research can provide guidline for transmission gear reliability design, high performance gear transmission design and manufacturing.