联合收获机切割器驱动装置减振设计与试验

Design and test on vibration reduction for knife driving device of combine harvester

为提高联合收获机割台的工作可靠性,构建了联合收获机切割器驱动装置力学模型,对平衡块安装位置和质量2个减振参数进行了理论计算.当曲柄轴转速为常用转速700 r/min时,计算得到最佳减振设计参数组合为平衡块质量1.677 kg,平衡块安装位置243°.在4LZS-1.8型联合收获机割台上进行振动试验,对滤波处理后的振动加速度测量值和惯性力计算值进行时间序列分析比较,验证了力学模型的准确性;最佳减振设计参数组合的减振比为66.3%,切割器驱动装置摇臂末端与切割器连接处的间隙是造成割台非线性振动的主要原因.为了明确由于长期使用导致间隙扩大造成振动加剧对减振设计参数的影响,构建了带间隙碰撞振动模型,分析了不同间隙距离的碰撞振动对减振效果的影响.结果表明,间隙大小不影响平衡块的安装位置,但间隙超过0.002 m时,驱动装置所受惯性力随间隙增大而增大.

Summary In the knife driving system of combine harvester,a slider-crank mechanism with a simple structure is used for driving the cutter bar.A low-cost balance mass is generally used in this mechanism to offset the unbalanced force for vibration reduction.The vibration characteristics of the knife driving system should be clarified in order to develop a method to reduce the vibration.Furthermore,it is necessary to develop a design theory of the knife driving system of combine harvesters in order to derive the control parameters of the balance weights used for vibration reduction. <br> The mechanical model of the knife driving device that is equipped with a slider-crank mechanism was constructed in order to derive the control parameters of the balance weights,such as the mass and the location of the balance mass.The simulation conditions of the model,which reflect the condition of the actual combine harvester, are listed.The angular velocity was equivalent to the rotation number of the crank wheel and was around 73 rad/s (700 r/min)in the clockwise direction.Vibration experiment was done with the type 4LZS-1.8 combine harvester.&nbsp;The vibration acceleration was measured using the preprocessing and cutting device of the actual combine harvester (the divider and conveying unit did not work;only the knife driving system worked).The interval time in calculation was set to 1 ms according to the sampling time of the measurement of the acceleration.The simulated inertia force was compared with measured acceleration in time series in order to evaluate the vibration model of the knife driving system.In the state without a balance mass,the simulation could express the vibration of the knife driving system well by comparing it with the measured acceleration.Consequently,this mechanical model could express the vibration characteristics of the knife driving system.The root mean square (RMS) value of the inertia force was simulated in the state with the balance mass in order to examine the effect of the vibration reduction. When the balance mass with 1.677 kg was attached at location 243°,the effect of vibration reduction due to the balance mass was confirmed to be best. <br> An interspace at the joint of the drive knife and the end of the link arm would increase in width because of the galling of the bearing and the gutter as the machinery was used.There was a nonlinear vibration caused by the interspaces between link arm and knife.The characteristics of the collision vibration system should be confirmed in order to clarify the vibration characteristics of the knife driving system of the combine harvester.The collision vibration model with interspaces was constructed;the effect of the increase in the width of the interspace on the vibration characteristics was investigated by simulating the collision vibration of the knife driving system.The width of the interspace was varied from 0.001 m to 0.005 m during the simulation,and the other parameters were the same as those of the foregoing simulation.The result showed that the effect of vibration reduction by the balance mass was confirmed irrespective of the width of the interspaces.When the width of the interspaces was 0.002 m or more,the simulated inertia force of the knife driving system increased with an increase in the width of the interspaces.