Simulation And Experimental Research On Drag Torque Characteristics Of High-speed Wet Multi-disc Clutch

The wet multi-disc clutch is widely used in large-scale construction machinery,heavyduty military vehicles and passenger car automatic transmissions due to its smooth,fast power transmission and excellent stability.The wet multi-disc clutch structure is composed of multiple annular friction plates It is composed of alternating distribution with the dual steel plates.When the vehicle is in the empty belt row,the friction plates are separated from the dual steel plates.In order to maintain good heat dissipation of the wet clutch,the cooling system uses forced circulation cooling lubricating oil to flow through the gap between the friction pairs to take away the heat and debris generated by friction in the gap between the friction pairs.The shearing effect produces drag torque and causes power loss of wet multi-disc clutches.Therefore,the analysis of drag torque of wet multi-disc clutches has always been a hot research topic at home and abroad.With the improvement of the working scene and performance of the vehicle,the use scene of the wet multi-plate clutch is gradually tending to the high-speed working condition,but there are few studies on the high-speed working condition of the wet clutch with drag torque.Therefore,this paper focuses on a new type of friction plate in the The research on the change of high-speed drag torque is mainly divided into the following parts:(1)The properties of the lubricating oil have an important influence on the performance of the wet multi-plate clutch.This paper establishes an improved viscosity-temperature characteristic equation for the viscosity-temperature characteristics of the lubricating oil,analyzes the characteristic parameters of the equation,and draws the viscosity-temperature characteristic of the lubricating oil with respect to temperature.According to the characteristic curve,it is known that the viscosity of lubricating oil decreases with the increase of temperature,and the viscosity decreases greatly with the increase of temperature at 0-30 ℃,and then it is relatively gentle.(2)In order to further study the causes and changing rules of the wet multi-disc clutch’s drag torque,a low-speed classic drag torque model was established,and the change rule of the low-speed drag torque was studied.Using the fluid N-S equation,the flow model of the friction pair gap flow field in cylindrical coordinates is established,and the oil film surface tension factor is considered to analyze the change of the equivalent radius of the oil film and the influence of air entering the friction pair gap after the oil film shrinks.Based on the characteristics of two-phase flow,an improved mathematical model of drag torque is established.Through the simulation calculation of the model and test parameter conditions,the influence of factors such as the flow rate and temperature of the lubricating oil,the rotational speed of the friction plate,the groove,the gap of the friction pair flow field and the size of the friction plate on the variation law of the high-speed drag torque is analyzed.(3)Based on the theory of fluid mechanics,the VOF model was established,and the fluid dynamic characteristics simulation of the gap oil film of the friction pair of the wet multi-plate clutch was carried out,and the law of the gap oil film of different groove types friction plate changing with the speed was analyzed,as well as the gap oil film of different groove types.The law of pressure changes.(4)Through the friction element high-speed drag torque test system,the drag torque test is carried out on the friction linings of three structures with different parameters.The relationship between drag torque and rotational speed was obtained,and the influence of parameters such as friction plate rotation direction,lubricating oil temperature and flow rate,and friction pair clearance on drag torque was analyzed.At the same time,the performance difference of the drag torque of the friction plates with different structures was compared by experiments and simulations.The results showed that the drag torque increased sharply with the increase of the speed,and then decreased rapidly after reaching the peak value,and then decreased with the increase of the speed.The increase showed a steady and slight upward trend.When the friction plate rotates counterclockwise,the peak clipping phenomenon occurs,and the maximum drag torque decreases relative to the clockwise direction,but in the high-speed stage,the counterclockwise drag torque will be greater than the clockwise drag torque.The lubricating oil temperature mainly affects the viscosity of the lubricating oil,thereby affecting the drag torque.With the increase of the lubricating oil temperature,the drag torque decreases.With the increase of lubricating oil flow,the drag torque increases,and with the decrease of the friction pair clearance,the drag torque increases.This conclusion verifies the accuracy of the model and simulation.