Investigation of dynamic characteristics of a valve train system

A valve train dynamics model of internal combustion engine has been developed using the kineto-elastodynamics method. The dynamics behavior for flexible components such as the valve springs in the valve train system was described by the wave equation. The contact force at the cam/tappet interface was estimated by the elasto-hydrodynamic lubrication theory of finite line conjunction. Component submodels were integrated into the whole valve train model by coupling the corresponding contact and friction forces, and solved simultaneously considering transient effect of lubrication, as well as the torsional and bending vibrations of camshaft. Experimental validation was performed on a motored test rig. The predicted results agree well with experiments at difference camshaft speeds. The effects of the bending deflection and torsional vibration of camshaft on performance of the valve train system were also studied.     

内燃机配气机构噪声控制

为降低内燃机配气机构振动噪声,以某125型摩托车发动机配气机构为研究对象,利用高次多项式对凸轮型线进行优化设计.配气机构多体动力学仿真表明:优化后的配气机构没有出现"飞脱"和"反跳"现象,进、排气气门丰满程度有所增加,在各个转速下,气门的最大振动加速度降低了65%左右,气门与摇臂的撞击力有所降低,且气门与气门座间的撞击力明显下降.在此基础上,制作了凸轮样件并对优化前后配气机构进行声功率测试试验.结果表明:在测量转速范围内声功率级均降低1.5～2dB.     

压缩空气动力发动机配气机构的研究

分析了气动发动机配气机构的特点，提出配气相位的设定必须考虑选择合适的膨胀率，以保证发动机动力性与工作效率的协调。对高压进气方式下配气机构的结构进行了研究，提出了两种能满足要求的结构形式，台架试验证明两种形式均能使气动发动机正常工作，其中气门外开式结构具有突出的优点，能更好地满足气动发动机的工作要求。     

内燃机故障的多重分形诊断方法研究

实测了6135柴油机气门机构处于不同状态时的缸盖振动信号,计算振动信号的多重分形维数,将其用于刻划缸盖在气门不同状态时表现的非线性行为,从而对故障分类与诊断。结果表明,当气门在不同状态时缸盖振动信号的多重分形维数是不同的,可以将其作为判断气门状态的依据。     

DYNAMIC MODEL AND SIMULATION OF A NOVEL ELECTRO-HYDRAULIC FULLY VARIABLE VALVE SYSTEM FOR FOUR-STROKE AUTOMOTIVE ENGINES

In modern four-stroke engine technology, variable valve timing and lift control offers potential benefits for making a high-performance engine. A novel electro-hydraulic fully variable valve train for four-stroke automotive engines is introduced. The construction of the nonlinear mathematic model of the valve train system and its dynamic analysis are also presented. Experimental and simulation results show that the novel electro-hydraulic valve train can achieve fully variable valve timing and lift control. Consequently the engine performance on different loads and speeds will be significantly increased. The technology also permits the elimination of the traditional throttle valve in the gasoline engines and increases engine design flexibility.     

新型十字摆盘驱动式水液压轴向柱塞泵阀配流系统设计

针对一种新型十字摆盘驱动式水液压轴向柱塞泵的配流阀系统结构参数与泵转速、柱塞直径不匹配导致的容积效率不足的问题,搭建了该新型泵的ADAMS-AMESim固液耦合仿真模型。在额定转速下,分析了配流阀阀芯质量、弹簧刚度、弹簧预紧力、阀芯球面直径对其容积效率的影响,并对其配流系统进行优化设计。结果表明:新型泵的容积效率随着配流阀弹簧刚度、预紧力的增加而增加,随着配流阀阀芯质量、阀芯球面直径的增加而减少,且吸液阀结构参数的变化对容积效率影响大于排液阀。因此,在设计新型泵的配流阀时可适当提高阀芯复位弹簧刚度和预紧力,适当减小阀芯质量和阀芯球面直径,以提高新型泵的容积效率。     

射流管三级电液伺服阀建模与动态特性仿真研究

叙述了射流管式三级电液伺服阀的结构及其工作原理,针对其结构建立了数学模型,并加入PD校正环节,导入MATLAB软件进行仿真,获得其阶跃响应曲线和开环伯德图。通过时域和频域分析表明,加入PD校正环节,使得系统局部相位超前,增加了系统的幅值裕度和相位裕度,因此其可大幅缩短三级阀的调整时间并增强其稳定性,同时反馈杆刚度和功率级滑阀阀芯面积对三级阀的动态响应有很大影响。通过有限元分析了圆形截面和矩形截面的反馈杆刚度,结果表明,在等面积时,由于矩形截面惯性矩大于圆形截面惯性矩,在相同的力作用下,矩形截面的反馈杆的位移较小,因此其反馈杆刚度较大,可提高先导级阀的动态反馈性能,从而更有利于三级阀的动态响应。     

基于谐波平衡法的复合行星齿轮传动系统非线性动态特性

为揭示多间隙作用下Ravigneaux型复合行星齿轮传动系统的非线性动力学行为,建立考虑时变啮合刚度、齿侧间隙与综合啮合误差的系统纯扭转强非线性动力学模型。将齿侧间隙非线性函数表达为描述函数的形式,运用谐波平衡法(Harmonic balance method,HBM)将方程组转化为非线性代数方程组,使用逆Broyden秩1法进行迭代求解,得到系统的基频稳态响应。通过改变时变啮合刚度、齿侧间隙与综合啮合误差的大小,分析参数变化对系统非线性动态特性的影响。研究发现,由于齿侧间隙的影响,系统动态特性曲线出现幅值跳跃与多值解等典型非线性特征,系统出现复杂的冲击现象;齿侧间隙、啮合刚度波动与误差波动的耦合使系统的非线性程度得以强化。基于描述函数的HBM法可用于求解更加复杂模型的基频稳态响应,为深入研究复合行星齿轮系统的动态特性提供了一种方法。     

地铁列车-嵌入式轨道系统动力学性能II：轨道参数对动力学性能影响

嵌入式轨道在地铁减振降噪方面具有广阔的应用前景，但仍然需要保证嵌入式轨道具备较好的动力学性能，因此开展其结构和材料参数对地铁列车-嵌入式轨道系统的动力学性能影响研究具有重要意义。基于建立的地铁列车-嵌入式轨道系统的动力学模型，分析承轨槽内填充材料特性、轨道板几何尺寸、轨道板下支承材料特性对系统动力学性能的影响，确定基于动力学性能的轨道参数优选范围。结果表明：填充材料垂向刚度的合理取值范围是每米80~110 kN/mm，填充材料横向刚度的合理取值范围是每米30~50 kN/mm，轨道板下支承刚度的合理取值范围是每平方米1~5 MN/mm。还分析了轨道板几何尺寸的合理取值范围。研究成果为地铁嵌入式轨道设计和参数选取提供了依据，从动力学角度为嵌入式轨道在地铁中应用提供了理论支撑。     

Transient elastohydrodynamic lubrication film thickness in sliding and rolling line contacts

The contact behavior between cam and follower is greatly influenced by the kinematics and dynamics of the whole valve train system. This is the reason that both shape and thickness of the fluid film in the contact gap are mainly determined by applied loads and relative contact speeds as well as the curvatures of contacting elements. Most of the studies about lubricant film behavior between cam and follower have been performed without a consideration of transient effects in the contact gap. For the computational difficulties of transient effects, most contact conditions such as relative contacting speeds have been regarded as quasi-steady state during the whole operating cycle. In this work, in order to obtain stable convergence, a multigrid multi-level method is used for the computation of load capacity in the lubricant film. Nonlinear valve spring dynamics are also considered in the same way as Hanachi’s. From the computational results, transient EHL film thicknesses under the conditions of different contact geometries are computed for a pushrod type valve train system during an engine cycle. Several results show the squeeze film effect, which is generally not found with conventional EHL computations of the cam and follower contact. The results are also compared with those by the Dowson-Hamrock (D-H) formula, which does not consider the dynamic film effect. Without the dynamic film effect as in D-H’s formula, the minimum film thickness is highly dependent on the entraining lubricant velocity, whereas the minimum film thickness including the squeeze film effect is dependent on the applied load.     

膜片式气制动阀静动特性

对我国拖拉机挂车气制动系主要控制元件之一—膜片式气制动阀静动特性做了理论分析和试验研究,通过适当改变气制动阀内部参数的方法,提高了其静动特性指标和拖拉机挂车机组的制动性能。试验表明气制动阀静特性不仅与几何尺寸、平衡弹簧刚度、输入气压及行程有关,还与制造精度、装配质量、调整误差有关,气制动阀的动特性不仅与平衡弹簧刚度有关,而且还与进气阀口内径和阀座硬度有关。     

基于增量谐波平衡法的星型齿轮传动非线性动力学分析

建立了两级星型齿轮传动系统的非线性动力学分析模型,模型中考虑了系统的综合啮合误差、时变啮合刚度以及齿侧间隙。推导了多自由度多间隙系统的增量谐波平衡法计算公式,利用上述方法求解了系统非线性微分方程组,得到了两级星型齿轮传动的非线性频响特性。分析了阻尼系数、时变啮合刚度以及误差等参数对系统动态特性的影响。分析结果表明:间隙会使两级星型齿轮传动系统中出现多值解及跳跃现象的典型非线性特征;增大系统阻尼系数可以抑制系统的共振幅值;增大时变刚度幅值使得齿轮副传动误差的幅值增大;增大激励误差的幅值,使得系统各构件的振动幅值增大;多级星型齿轮传动系统有着比单级传动更丰富的非线性动态特性。     

Dynamic Modeling of Floating Valve Plate Motion in an Axial Piston Pump

The objectives of this study were to analytically and experimentally investigate the motion of the floating valve plate in an axial piston pump under various operating conditions. To achieve the objectives of the analytical investigation, the equations of motion for the valve plate were coupled with a time-dependent lubrication model. The balance pistons that support the floating valve plate were represented by equivalent spring and dashpot systems. The system of equations was then solved using the Runge-Kutta and the control volume finite difference methods to determine the pressure, film thickness, and motion of the valve plate for various operating conditions. To achieve the experimental objectives, a previously developed axial piston pump test rig was instrumented with proximity probes to measure the motion of the valve plate. The stiffness and damping of the balance pistons supporting the floating valve plate were determined using the impact and frequency response methods. Using the experimentally determined stiffness and damping coefficients in the coupled dynamic lubrication model, the analytical and experimental results of the valve plate motions were compared. The model was then used to conduct a parametric study to determine the overall system stiffness and damping coefficients during pump operation. Using the stiffness and damping coefficients from the parametric study in the dynamic lubrication model, the pressure, film thickness, and motion of the valve plate were calculated for various operating conditions. The experimental and analytical displacements of the valve plate were then corroborated and found to be in good agreement.     

电液驱动可变气机构缓冲过程研究

电液驱动可变气门机构缓冲过程影响气门机构的冲击性能及气门运动的响应性能。基于AMESim仿真软件,设计了电液驱动可变气门系统,研究了节流阀节流面积和节流行程对气门运动缓冲过程的影响规律,并采用遗传算法对节流阀控制参数进行寻优,改善气门运动缓冲性能。结果表明,减小节流行程和增大节流面积可以提高气门运动的响应性能。通过遗传算法对控制参数进行寻优,在优化的控制参数下气门行程终了速度明显改善,气门开启至最大行程时速度降至0.11m/s,气门关闭落座速度降至0.07m/s,同时保证气门运动的响应性能。     

Oil Degradation in a Diesel Engine with Dual-Loop Lubricating System

A common lubricating oil sump is used in most modern internal combustion engines for cooling, wear protection, and friction reduction. This requires compromises during base oil and additive selection as a result of differing needs for lubricant performance in engine subsystems. The use of a dual lubricating loop, providing separate oil sumps for the power cylinder and valve train subsystems, was investigated experimentally to determine the effect of system segregation on oil degradation. A small diesel engine was modified, installed in a commercial generator unit, and operated for one oil drain cycle. Oil sampling was tailored to assess base and acid numbers, oxidation, soot concentration, water content, and viscosity changes. The experiment complemented an earlier study that investigated the fuel economy benefits of such a lubricating configuration. These include longer drain intervals for the cylinder head and power cylinder subsystems, improved wear performance for the valve train, and opportunities for alternative material selection during engine design. The experiment demonstrated protection of the valve train subsystem from soot contaminants in the power cylinder. Lower total acid number and oxidation tendency was also observed in the valve train.     

变刚度弹簧往复泵锥阀及其动态特性仿真

设计了变刚度弹簧往复泵自动锥阀,弹簧刚度是阀盘升程的函数。在阿道尔夫泵阀运动微分方程的基础上,考虑流体可压缩性对泵筒内流体连续流条件的影响,建立了变刚度弹簧往复泵自动锥阀阀盘运动规律的微分方程。以弹簧刚度是阀盘升程的线性函数为例,分析了变刚度弹簧往复泵锥阀阀盘的动力特性。仿真结果显示：弹簧刚度随升程的变化规律对阀盘的动力特性具有显著影响;在阀盘最大升程一定的条件下,与定刚度弹簧阀盘的动力特性相比,减函数变刚度弹簧阀盘的落座速度与滞后高度有所下降,有利于提高往复泵的容积效率,提高阀盘与阀座的疲劳寿命。     

提高多级齿轮传动系统动态性能的优化设计

提出了提高多级斜齿圆柱齿轮传动系统动态性能优化设计方法。重点论述了系统动力学模型的建立,运动微分方程的求解方法和优化数学模型。由于系统动力学模型考虑了多对齿轮的转动惯量、时变啮合刚度、误差、阻尼以及轴的转动惯量和刚度,因此,所建立的微分方程式是多自由度时变方程组,对此,本文采用模态分析法与状态空间法相结合的方法进行求解。在此基础上,建立了提高齿轮传动系统动态性能优化设计的数学模型。实例计算证明,动态性能优化设计后的齿轮传动系统,其动态性能有明显的改善。     

基于实测数据的车轨耦合模型更新方法

提出了一种适用于车轨耦合系统的模型更新方法,其更新过程主要由两大步骤来实现:a.更新列车运行速度;b.更新扣件刚度。首先,建立了地铁列车车轨耦合系统模型,采用迭代的方法求解系统动力响应;其次,选取地铁普通整体道床轨道线路开展测试以获得现场实测数据,随后利用车轨耦合系统模型发现钢轨位移动力响应受扣件刚度影响较为明显,而受扣件阻尼影响较小。更新列车运行速度的主要目的是使激振主频更加吻合现场实测状况,在此基础上更新扣件刚度可使频域幅值更为接近。钢轨位移动力响应的频谱由列车周期荷载的一阶多次频率控制,这是由于轨道结构的多点连续支承特性所造成的。通过对比模型更新后的模拟结果与测试结果,验证了所提模型更新方法的可行性。研究结果表明,更新列车运行速度及扣件刚度是进行地铁列车与轨道耦合系统模型更新的有效方法之一。     

负遮盖四通伺服阀的静特性分析

本文根据功率匹配原则,定义了对称阀控不对称缸系统的负载压力和负载流量,并对一应用于并联式液压平台的负遮盖伺服阀进行了静特性分析,认为阀的特性同其所处系统的结构有关;另外,相比于零遮盖伺服阀,负遮盖阀由于预开口的存在,增加了阀的中位泄漏,降低了系统的输出刚度,但明显提高了阀压力－流量特性曲线的线性度,提高了系统的稳定性。     

面向足式机器人的P-Q阀控非对称液压缸位置闭环刚度特性研究

大负载足式机器人一般选用液压驱动单元作为系统的驱动机构。考虑到机器人结构紧凑性及控制性能等原因,研究了一种基于P-Q阀控非对称液压缸系统的位置闭环刚度特性。通过建立并利用系统的非线性方程,结合P-Q阀的特性,研究了P-Q阀在位置闭环时等效刚度动静态特性。研究表明,在位置闭环时,系统特性与弹簧等效且等效刚度与系统的增益成正比,这为机器人基于位置闭环的阻抗控制提供了理论基础。