Theoretical Study And Experimental Analysis For Transmission Gear's Fault Of Car

There were two problems of transmission's gear of car in the course of the type experiment. The first problem is that the vibration of gears was changed as the temperature of lubricant. The second problem is that the edges of gear where contact with the shaft cracked. The paper analyzes the reasons of the two problems. The main contents are as follows:(1) When the viscosity of lubricant changed, the stiffness of damp of meshing faces changed. So the vibration amplitude changed. Considering the characters of helical gear, the paper replaced mean equivalent curvature radius with equivalent curvature radius. The paper proposed a model of gear meshing based onгрубин's hypothesis for the height of oil film between two cylinders. And then, the paper constructed a model of the hydrodynamic lubricant of gear system by considering the facts viscosity and pressure of lubricant. Analyzing the model by numeric simulation, the result shows that the amplitude of vibration of gear system increases with the reduction of lubricant viscosity and the viscosity smaller the slope of the curve bigger. The test was carried out to prove the numeric simulation, and the result of test was similar to its.(2) The paper analyzed the pressure state at the contact face and the stress state of gear and shaft which is interference-fit joint by FEA, and got the relationships between contact diameter, contact width, interference value and the most stress at contact margin of gear and shaft. The tradition way ignores the stress concentration at the edges of gear where contact with shaft, which result in the stress of the edges may exceeds the gear's yield stress limits. In addition, the paper constructs the BP model which was trained by the data of 360 groups's stress at the contact margin of gear and shaft by FEA; and tests the BP model which the largest deviation is 1.61%. The dynamic regulating parameter based on BP was proposed to devise the interference-fit joint of gear and shaft. At last, comparing the traditional way and the dynamic regulating parameters based on BP by calculating example, the result shows that the latter was more convenient and precision.