Design and test on vibration reduction for knife driving device of combine harvester
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 drivin...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Zhejiang University Press
2014-09-01
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| Series: | 浙江大学学报. 农业与生命科学版 |
| Subjects: | |
| Online Access: | https://www.academax.com/doi/10.3785/j.issn.1008-9209.2014.01.076 |
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| 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.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. 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.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. |
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| ISSN: | 1008-9209 2097-5155 |