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Shudder in continuously slipping wet clutch (CSWC) systems is an instability that manifests itself as a vibration of the automobile's drive train. Dynamometer experiments imply that the shudder is connected to degradation of the frictional properties of the clutch friction material-automatic transmission fluid (ATF) system. The poor friction characteristics are revealed in negatively sloped torque vs. slip-speed curves which can result in dynamic friction oscillation instabilities. The authors report local measurements of friction vs. velocity with the use of a scanning force microscope (SFM) on new and glazed wet clutch friction material with either new or degraded ATF acting as a lubricant. The friction material was a commonly used cellulose/phenolic resin material. Results in the very low-speed dynamic regime indicate that the fluid condition plays a critical role in determining the slope characteristics of the friction vs. velocity curve. ATF degraded in service imparts a flat or negative slope to the friction vs. velocity curve, whether on new or glazed (degraded) friction material. A positive slope is measured for fresh ATF. The SFM measurements are therefore consistent with dynamometer and vehicle experiments which measure gross properties of the friction clutch system. The ability of the SFM to reproduce the dynamometer results on a local scale implies that shudder is not due to the gross fluid flow or mechanical effects that are present in a complete torque converter. The frictional characteristics of the clutch plate materials and the ATF are paramount. This technique allows continuous monitoring of ATF fluid degradation in test fleet vehicles without ATF replenishment since only a few ccs of fluid are necessary for these tests. 相似文献
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Mikael Holgerson 《Lubrication Science》2000,7(2):99-114
To optimise the gear change in automatic transmissions, more knowledge is needed of the engagement behaviour of wet clutches. A factorial design investigation of the engagement of a wet clutch has been carried out. The friction and temperature characteristics have been studied. The experiments were carried out in an apparatus that can vary sliding velocity, drive torque, inertia, force rate, and lubricant flow. The results show how these parameters affect the response data: engagement time, developed energy, temperature rise, maximum torque, maximum power, static friction, dynamic friction, and initial friction. There are interaction effects between some of the input parameters, but they are relatively small. The friction coefficient varies over time but is independent of the input parameters, except for dynamic friction, which decreases with increasing sliding velocity, drive torque, and inertia. The temperature rise was found to be proportional to developed energy and both these were most affected by sliding velocity. The drive torque and force rate have the greatest effect on the engagement time. 相似文献
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针对湿式离合器试验过程中磨合状态的预测问题,提出利用摩擦转矩信号分形特征来预测和评价磨合状态的新方法.首先,分别阐述了摩擦转矩信号盒子维数和关联维数的计算方法;然后,在湿式离合器试验台上提取了磨合试验的摩擦转矩信号,并对信号进行了自相似性分析;最后,应用盒子维数和关联维数分别对摩擦转矩信号进行了分形研究.分析结果表明:盒子维数和关联维数都能定量描述试验过程中摩擦转矩信号的分形特征,随着磨合次数的增加,摩擦转矩信号的盒子维数和关联维数的波动范围都逐渐减小,并且最终收敛于较小的波动范围.因此,利用试验中摩擦转矩信号的分形特征能够在不开箱条件下定量地预测和评价湿式离合器的磨合状态. 相似文献
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Keiji Imado Hiroki Tominaga Atsuyoshi Miura Yasuaki Yamaguchi Tsuneo Kawagoe 《Tribology International》2010,43(5-6):1127-1131
A novel clutch was developed by using the self-locking property of belt friction. The frictional force is generated automatically by the torque applied. The belt starts to coil around the cylinder by the frictional force of the trigger pin at the end of the belt. Once the belt comes in contact with the cylinder, the belt coils automatically around the cylinder by the frictional force. Then the belt is locked firmly around the cylinder by the self-locking property of belt friction as long as driving torque is applying. The clutch is able to transmit rotational torque even in an off-centered condition. 相似文献
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Wet clutches are used in automatic transmissions to enable gear changes and also to reduce energy loss in the torque converter.
These friction devices are susceptible to stick–slip effects, which result in the vehicle giving an unsteady ride. Stick–slip
effects can be avoided by ensuring the wet clutch and lubricant combination produces a friction coefficient that increases
with sliding speed. Although wet clutches have been studied throughout the industry for many decades, the mechanism of the
generated friction is still not fully understood. It is known that, because of the fibrous nature and thus very large roughness
of friction material, the overall contact between clutch plates actually consists of many small, independent, contact units,
which are the sites of the generated friction. Some authors have suggested that a temperature rise due to friction either
at these contact units or of the overall clutch plate may be important in controlling friction behaviour. In this study, the
flash temperatures at the contact units formed in the wet clutch contact have been measured using an infrared camera. Three
friction materials have been tested. It was found that measured flash temperature in a pure sliding system similar to that
present in a slipping clutch remain well below 5 °C, and are therefore unlikely to play a major role in the observed friction-speed
dependency of slipping wet clutches at speeds below 2 m/s. 相似文献
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离合器摩擦副表面温度对摩擦因数的影响 总被引:2,自引:0,他引:2
通过对某型离合器摩擦副的摩擦学小样试验,研究了离合器在结合的滑动摩擦过程中,摩擦面温度对离合器摩擦材料摩擦因数的影响.采用扫描电子显微镜(SEM),分析了样件的摩擦表面形貌,探讨了产生影响的机制,并从摩擦因数角度探讨了微车离合器起步发抖和烧蚀的主要原因.微车离合器摩擦材料摩擦因数随着摩擦面温度先升高,然后趋于稳定,最后再降低,其稳定工作的温度区间为130~220℃;在摩擦面温度较低的工况下,摩擦因数较低,微车起步时,离合器传递的扭矩不足以克服道路阻力,引起微车起步发抖的现象;而在摩擦面温度过高的工况下,离合过程中,摩擦因数较低,传递扭矩效率低,导致离合器滑磨时间过长,引起烧蚀现象. 相似文献
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随着人们对汽车舒适性的要求不断提高,提高减振效果、减少传动系的噪声是汽车制造业迫切需要解决的问题.本文设计了一种新型大转角减振离合器,采用偏心凸轮摩擦阻尼减振系统结构,依靠偏心力矩和摩擦力矩传递扭矩,利用钢板弹簧的弹性变形代替普通弹簧,增加扭转角度.该离合器结构紧凑、加工工艺简单,提高了接合平顺性和乘客的舒适度. 相似文献
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汽车风扇离合器不仅是汽车节能的重要措施之一,也是保证汽车发动机在最佳温度下工作的温控系统。所以,离合器的性能好坏,直接影响发动机的正常工作。为提高汽车风扇离合器的产品质量,保证运行可靠性,我们参照“汽车硅油风扇离合器验收标准”,研制了汽车硅油风扇离台器全性能微机综合检测系统。试用结果表明,整个系统设计合理、可靠、手段先进,实现了自动在线综合检测,提高了工作效率和检测精度。 相似文献
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Numerical study is performed of the effect of the inertial force parameters on the thermal conditions of a multidisc oil-cooled friction clutch of a rear power take-off shaft of a power-intensive wheel tractor. A system of differential equations is shown of the dynamics of slippage of the driven and driving disks when the clutch is actuated and it is solved numerically with the Runge-Kutt method. An initial boundary problem is formulated describing the thermal processes in the package of disks when friction heats the clutch; it is solved numerically with the finite elements method. 相似文献
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离合器是汽车传动系统的重要组成部分,其接合过程直接影响到车辆起步性能和动力传递,并影响系统各单元的使用寿命。针对离合器接合过程的特点,对滑摩状态和接合状态进行动力学分析,建立系统的动力学模型;从滑摩功和冲击度两个方面对离合器接合过程进行评价,获取影响换挡品质的评价指标因素;根据动力模型和数学模型,基于Simulink建立离合器接合过程的分析模型;研究不同坡度及载重等因素对离合器接合过程中摩擦片的角速度、滑摩功及冲击度的影响,获取各因素的影响规律。结果可知:随着油门开度和油门变化率的逐渐增大,离合器接合角速度和接合时间都有所增大,接合过程产生的滑摩功也不断增多;随着起步坡度、载重的增大,离合器接合角速度逐渐减小,接合时间逐渐增大,接合过程产生的滑摩功也不断增多;分析过程和结果为此类设计提供参考。 相似文献
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针对常用机械式自动变速器(automated mechanical transmission,AMT)起步控制策略由于将离合器动摩擦系数视为常量,而忽略其变化所导致的车辆起步冲击度大的问题,对某款微型车AMT的起步过程进行了研究,提出了基于动摩擦系数的微型车离合器起步接合过程的动力学研究方法,根据摩擦学原理及其试验,讨论了离合器动摩擦系数随转速变化的关系,建立了离合器三维实体模型,并利用ADAMS软件对离合器起步接合过程进行了动力学仿真,分析了干式膜片弹簧摩擦离合器的动摩擦系数与其摩擦力矩和冲击度的关系。研究结果表明,与动摩擦系数为常量的离合器相比,动摩擦系数为变量的离合器半接合点和同步点的冲击度更大。其中,半接合点的冲击度增加率为110%,验证了动摩擦系数变化对车辆起步冲击度作用的重要性。 相似文献
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针对摩擦焊设备的机构繁琐、庞大的缺点,文中选用合适的变频电机为动力源,代替了复杂的传动装置和制动离合装置,通过联轴器直接将动力传递到机床主轴上,同时选用合适的液压缸、联轴器和轴承座,并设计出合理的机床主轴和液性塑料夹具,使摩擦焊机的结构设计更加合理,布局更加紧凑。 相似文献
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润滑油温度对铜基湿式离合器摩擦转矩的影响 总被引:2,自引:0,他引:2
润滑油的温度变化会改变自身黏度,从而影响摩擦元件的润滑和接触状态,对离合器的动力响应产生显著影响,因此需要研究润滑油温度对湿式离合器摩擦转矩特性的影响。考虑离合器的流体润滑、粗糙接触、动力响应和热量传导,建立一个多物理场耦合的热力学模型;根据润滑油与离合器之间的换热特性,采用集总参数法得到离合器的平均温升。离合器台架试验验证所建立数值模型的准确性。结果表明在离合器的接合过程中,摩擦转矩的变化可分为三个阶段,即接合准备阶段A、缓慢变化阶段B和指数增长阶段C。润滑油温度主要影响阶段B的摩擦转矩。在阶段B早期,润滑油温度越高,黏性转矩越小,接触转矩越大。随后,润滑油温度的升高减缓黏性转矩的下降趋势,促进接触转矩的增加,从而促进摩擦转矩增长率的增加。为了保证离合器在阶段B的摩擦稳定性,最佳的润滑油温度范围为80~100℃。 相似文献
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Numerical and Experimental Studies of a Wet Multidisc Clutch on Temperature and Stress Fields Excited by the Concentrated Load 总被引:1,自引:0,他引:1
The outer circlip constraint is a typical way for a wet multidisc clutch to limit the axial displacement of friction components. The pressure transmission mechanism in a clutch, excited by the concentrated reactive force of the outer circlip, is revealed by a simplified pressure calculation model. Moreover, a finite element model is constructed to investigate the contact pressure distributions on friction surfaces. Thermal analysis to determine the radial temperature distributions on friction surfaces is performed numerically. The computational results indicate that the concentrated reactive force contributes to the dissimilar distributions of the contact pressure along the radial and axial directions. The radial contact pressure considerably affects the temperature fields on friction surfaces, which is verified effectively by bench tests under the creeping condition. Both simulation and experimental results demonstrate that the outer circlip is identified to be one of the main reasons for the expansion of the radial temperature difference. In order to smooth the contact pressure in the radial direction, three new designs for a circlip are proposed, including an inner circlip, medial circlip, and both inner and outer circlips. Considering the utility and feasibility of the four cases, the design with both the inner and outer circlips is the most appropriate one. 相似文献