Simulation And Parameter Influence Analysis On Churning Power Loss Of Transmission

Most of the vehicle transmission uses gear transmission,and splash lubrication is the most commonly used lubrication mode in the middle and low speed range.The gear immersed in lubricating oil will cause churning power loss during the working process.Reducing the power loss of the meshing gear can significantly reduce the power loss of the transmission and improve the efficiency of the transmission,reduce the heat production of the transmission and improve the working life.In this paper,the computational fluid dynamics(CFD)method is used to simulate and analyze the power loss of a DCT transmission.The work and main conclusions are as follows:(1)The dynamic grid method and sliding mesh method are used to simulate the churning power loss of single spur gear.The results show that the simulation results of the dynamic grid method is more accurate to study the power loss of the meshing gear.At the same time,the simulation analysis is made on the power loss of single gear churning oil with different parameters,such as speed,air pressure in the box,viscosity of lubricating oil,tilt angle of oil tank,helix angle of gear,oil volume and so on.The results show that the churning power loss increase with the gear speed,the air pressure in the box,the helix angle of the gear or the volume or viscosity of the lubricating oil.(2)The model of meshing gear churning is modeled by single-cutting-teeth method,gear-separation method and teeth-face-moving method.The compare of the simulation results of the power loss of the meshing gear and the test results show that the teeth-facemoving method has high accuracy and good engineering adaptability,and is suitable for modeling of meshing gears.At the same time,the influence of rotating speed,rotation direction and transmission ratio on the churning power loss of meshing gear is studied.The results show that the churning loss increases when the gear speed increases or the transmission ratio increases,and the churning loss when the rotation is counter-clockwise is greater than the clockwise rotation.(3)Change the axial distance and radial distance between the gear to the body of the box and the rectangular box and the flange,and study the influence of the structure shape of the box on the churning loss of the meshing gear.The results show that when the radial distance or the axial distance of the gear to the wall of the box is reduced,the churning loss of the meshing gear increases.When the radial distance of the gear to the baffle decreases,the churning loss of the meshing gear increases.The axial distance of the gear to the flange decreases and the oil loss of the meshing gear decreases.When there is a baffle and the axial distance of flange is reduced,the churning loss of meshing gear increases.(4)A simulation model of gas and liquid two phase flow field inside a DCT transmission is established based on Fluent software.The simulation analysis is made on the transmission churning in the 4 gear 1900r/min,6 gear 2200r/min and 7 gear 2980r/min.And the flow field distribution and the churning power loss are obtained,and the results are compared with the often used empirical formula calculation results.The result shows that the formula(1.1)of the 4 gear 1900r/min is close to the simulation result,and the formula(1.4)of the 6 gear 2200r/min and 7 gear 2980r/min is more accurate.