The experimental results of ZHY gear only verify the correctness of the calculation method of tooth contact temperature under EHL condition, but not the other three conditions. The establishment of numerical calculation method and experimental work of tooth contact temperature in EHL is the basis of verifying the calculation method of tooth contact temperature in mixed lubrication, boundary lubrication and dry friction.
(1) Based on the theory of Blok flash temperature, the expression of the instantaneous temperature of the tooth surface is obtained. The expression of the contact temperature of the tooth surface in four different states is derived from the friction coefficient of the tooth surface in four different states. At the same time, the experimental measurement under different working conditions was carried out.
(2) Through numerical calculation and experimental measurement, the dynamic effects of rotating speed and torque on tooth contact temperature are analyzed. The results show that the contact temperature increases with the increase of speed and torque. The contact temperature of the tooth surface is the highest at the meshing position and the top of the tooth, which is more likely to cause the tooth surface gluing, and it is close to the room temperature near the joint. The conclusion is consistent with the existing research results, which shows that the calculation method of tooth surface contact temperature in this paper can reflect the change of tooth surface contact temperature when the gears are engaged to a certain extent, and its basic law is correct and scientific when calculating the change of tooth surface contact temperature.
(3) It is found that the influence of system parameters on tooth contact temperature is not the same in four different states. In elastohydrodynamic lubrication, the contact temperature of tooth surface increases with the increase of speed or torque and viscosity of lubricating oil, while in mixed lubrication, the contact temperature of tooth surface increases with the increase of speed or torque and the decrease of viscosity of lubricating oil. Under the condition of boundary lubrication and dry friction, with the increase of rotating speed or torque, the increase of tooth contact temperature is obvious, but the effect of lubricant viscosity on tooth contact temperature can be ignored. Therefore, in order to prevent the occurrence of the gluing defect on the gear surface when meshing, the viscosity of the lubricating oil should be changed according to the actual situation. At the same time, it is found that the backlash has little effect on the contact temperature of the tooth surface, but the increase of backlash will cause the impact of the tooth surface and generate large noise, so it is necessary to choose a reasonable range in practical engineering application.
(4) In order to show more clearly the same point and difference of the change rule of tooth surface contact temperature of gear system in different lubrication environment under the same parameter coupling change, the influence rule of coupling change of four lubrication conditions (including elastohydrodynamic lubrication state and mixed lubrication state) parameters on tooth surface contact temperature is compared. It is also found that the gear system is in better EHL state, because the contact temperature of gear tooth surface in EHL is lower under the same working condition, which is more conducive to the operation of the gear and prolong the service life.