【作者】 马超；

【导师】 李杰； 兰海；

【作者基本信息】 北京建筑大学 ， 机械工程（专业学位）， 2023， 硕士

【摘要】 湿式多片离合器因其平稳、快速的动力传递,出色的稳定性,广泛应用于大型工程机械与重载军用车辆和乘用车自动变速箱上,湿式多片离合器结构是由多个环形摩擦片与对偶钢片交替分布组成,当车辆处于空载带排时,摩擦片与对偶钢片分离。为保持湿式离合器良好的散热,冷却系统为强制循环冷却,润滑油流经摩擦副间隙,带走摩擦副间隙的热量与摩擦产生的碎屑,当流经间隙时摩擦片的转动会对润滑油产生剪切作用,产生带排转矩,造成湿式多片离合器功率损失,因此对湿式多片离合器的带排转矩分析一直是国内外研究的热点。随着车辆工作场景与性能的提升,湿式多片离合器的使用场景逐渐趋向于高速工况,而对于湿式离合器带排转矩高速工况的研究目前较少,因此本文针对一种新型摩擦片在高速带排转矩的变化进行研究,主要分为以下部分:(1)润滑油的性质对于湿式多片离合器的性能有着重要影响,本文针对润滑油的粘温特性,建立改进的粘温特性方程,对方程特征参数进行分析,绘制润滑油关于温度的粘温特性曲线,根据曲线得知润滑油粘度随温度的增大而减小,在0-30℃粘度随温度增加下降较大,之后较平缓。(2)为深入研究湿式多片离合器带排转矩的产生原因以及变化规律,建立低速经典带排转矩模型,对低速带排转矩的变化规律进行了研究。利用流体N-S方程,建立圆柱坐标下摩擦副间隙流场流动模型,考虑油膜表面张力因素,分析油膜等效半径的变化,和油膜收缩后空气进入摩擦副间隙的影响,基于高转速状态下的油气两相流特征,建立改进的带排转矩数学模型。通过模型与试验参数条件进行仿真计算,分析了润滑油的流量、温度,摩擦片转速、沟槽,摩擦副流场间隙与摩擦片尺寸大小等因素对高速带排转矩变化规律的影响。(3)基于流体力学理论,建立VOF模型,并对湿式多片离合器摩擦副间隙油膜进行流体动态特性仿真,分析不同槽型摩擦片间隙油膜随转速变化的规律,以及不同槽型的间隙油膜的压力变化规律。(4)通过摩擦元件高线速带排试验系统,对不同参数的三种结构摩擦片进行带排试验。获得带排转矩与转速的变化关系,分析了摩擦片旋转方向、润滑油温度与流量、摩擦副间隙等参数对带排转矩的影响。同时对不同结构的摩擦片带排转矩性能差异,进行了试验与仿真对比,结果显示,带排转矩随转速的增加呈先急剧增大,达到峰值后又快速减小,然后随转速的增大呈平稳且轻微上升趋势。摩擦片逆时针方向旋转时出现削峰现象,带排转矩最大值相对顺时针减小,但在高速阶段,逆时针带排转矩会大于顺时针带排转矩。润滑油温度主要会影响润滑油的粘度,从而对带排转矩造成影响,随着润滑油温度的增大,带排转矩降低。随着润滑油流量的增大,带排转矩增大;随着摩擦副间隙的减小,带排转矩增大,该结论验证了模型与仿真的准确性。更多还原

【Abstract】 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.更多还原