某轻卡驾驶室怠速抖动原因及改进

Causes of the idle jitter of a light truck′s cab and its improvement

为解决某轻卡空压机工作引起的驾驶室怠速抖动问题,测试座椅、发动机和空压机的振动加速度,分析怠速工况下驾驶室抖动的激励源、动力总成悬置系统隔振和空压机往复惯性力,通过仿真和试验结合设计改进方案,并进行试验验证。结果表明:空压机振动是驾驶室抖动的激励源,空压机工作频率与动力总成多个刚体模态的固有频率接近,振动隔振效果差;降低空压机往复惯性质量、优化曲轴过量平衡率降低空压机本体振动,确定最佳过量平衡率为0.25;将传动速比由0.68增大为1.00,空压机工作频率由8.5 Hz提高到12.5 Hz;优化后,怠速工况下座椅的振动加速度幅值由0.044 g(g为自由落体加速度)降低至0.019g,达到客户主观评价要求。

To find out the problem of cab idle jitter from the operation of a light truck air compressor,the vibration acceleration of the seat,engine and air compressor is measured.The excitation source of cab jitter under idle conditions,the vibration isolation of the powertrain suspension system,and the reciprocating inertial force of the air compressor are analyzed.An improvement scheme is designed via simulation and experimentation,and test verification is performed.The results indicate that the vibration of the air compressor serves as the driving source of cab jitter.The operating frequency of the air compressor approximates the natural frequencies of several rigid body modes of the powertrain,thus leading to a poor vibration isolation effect at this frequency.By decreasing the reciprocating inertia mass of the air compressor and optimizing the excess balance rate of the crankshaft,the vibration of the air compressor body can be reduced,and the optimal excess balance rate is determined to 0.25.By increasing the air compressor speed ratio from 0.68 to 1.0,the operating frequency of the air compressor has been increased from 8.5 Hz to 12.5 Hz.After the optimization,the vibration acceleration amplitude of the seat under idle condition has been decreased from 0.044 g to 0.019 g,fulfilling the subjective evaluation requirements of customers.