The Influence Of Front Axle Suspension On Tractor Vibration Characteristics

Compared with cars, buses and trucks, the tractor has a long time driving in the field and the dirt road of rural, the vibration reducing device is simple, the vibration is particularly acute. Severe vibration of tractor not only can cause serious harm to the health of the driver,but also can cause the fatigue damage of the components, which seriously affect the service life of the tractor. In addition, the excessive vibration of the tractor will also aggravate the compaction of the soil and reduce the yield of crops. How to effectively reduce the vibration of tractor, improve the comfort and safety of the tractor and reduce the damage to the agricultural land is an important research topic for scientific research personnel and tractor manufacturing enterprises. Considering the manufacturing cost, the basic domestic tractor equipped with no front axle suspension system, the related research is rarely reported. In order to clarify the installation axle suspension of tractor vibration influence.The main work and research results are summarized as follows:1. Taking the CF700 tractor as the research object, using the method of real vehicle test, the vibration characteristic parameters of the vibration acceleration, the vibration acceleration of the fuselage, the seat vibration acceleration and the front and rear wheel dymamic loads were detected.Analysis of the time domain and frequency domain is carried out by the test results, determined the natural frequency of vertical vibration and pitch vibration of tractor,and the vibration acceleration power spectrum density of the fuselage, front and rear axle and seat mounting is plotted.The road surface roughness was measured by the Jiangpu farm of Nanjing Agricultural University and 100m Standard Test Center of the Jiangsu agricultural machinery testing center.The power spectrum density of pavement is analyzed and calculated,it was concluded that the road conditions of the Jiangpu farm soil road and the 100m Standard Test runway are similar, the grade is the national standard D grade pavement.2. Established the physical model and theoretical model of no suspension tractor 2DOF vibration system, through theoretical analysis, derive the theoretical tractor after no suspension system decoupling natural frequency of vibration is calculated and body vibration acceleration, seat vibration acceleration theoretical dynamic vibration characteristics of the front and rear load and other formula, by theoretical calculation and the actual vehicle test data for comparison, tractor show real vehicle test data and theoretical calculations the minimum error rate 3.09%, the maximum error rate in 12 %,indicating that the actual vehicle test data and theoretical error rate of the data within an acceptable range, indicating that the theoretical calculations can better reflect the tractor's vibration characteristics, prove the reliability and feasibility of the theoretical analysis. On this basis, the study of the vibration characteristics of the suspension without tractor driving conditions in the marshy soil of paddy field. Found that when a tractor in rural dirt road driving conditions (GB D level road) for driving the vibration characteristics of a tractor in the marshy paddy soils with different non-coverage, which compared to the previous vertical vibration,displacement transfer rate of the rear wheel fell 31.4 respectively % and 23.5%, respectively 29.5% decline pitching vibration and 24.6%; body vertical acceleration and angular fuselage pitching vibration reduced by an average of 33% and 32.6%; front and rear dynamic load an average of 34% and 31.2%; seat-mounted vertical vibration acceleration at an average of 32.9%. The results of this study can be used as the basis of dual-use rice fields Tractor damping system design and intelligent control.3. Established the physical model and theoretical model of front axle suspension tractor 3DOF vibration system, theory calculation formula of axle suspension tractor vibration characteristics, and the stiffness and damping coefficients of front axle suspension are optimized to match, the study found mounted on the front axle suspension frame of the tractor when using the optimized axle suspension stiffness and damping coefficients, the body vertical vibration acceleration and pitching vibration angular acceleration and suspension front axle to compared respectively, the average fell 24.03% and 42.46%; seat installed in the vertical direction vibration acceleration dropped by an average of 29.77%;front wheel dynamic load dropped by an average of 21.72%. Analysis results show that a tractor mounted axle suspension, the vertical vibration acceleration and pitching vibration acceleration to have different degrees of decrease, especially the lower tractor pitch vibration acceleration is particularly significant, improve the ride comfort of the tractor.The sharp drop of the front wheel dynamic load makes the steering wheel 's out of the ground probability greatly reduced, and the safety of the tractor is improved. The research results have certain reference value on optimization design of tractor vibration system and axle suspension system.4. Established the physical model and theoretical model of front axle suspension plus seat suspension tractor 4DOF vibration system.Analysis of the natural frequency and amplitude-frequency characteristics of the fuselage, seats and front and rear axle with front axle suspension 4DOF vibration tractor seat suspension system for road excitation, and found the front axle suspension plus seat suspension 4DOF tractor vibration system body vertical vibration and pitch vibration natural frequency compared to the front axle suspension 3DOF tractor vibration system change is very small,the maximum change rate was 2.7%, indicating that the installation of seat suspension afrter the natural frequencies of the vibration system of tractor changes very little can be neglected. And deduced the front axle suspension coupled with the tractor seat suspension 4DOF vibration system fuselage vibration acceleration, vibration acceleration of seat, a front wheel and a back wheel dynamic load and seat suspension dynamic deflection and vibration characteristics of the index theory calculation formula. Study found that 1) compared with the front axle suspension tractor 3DOF vibration system, the installation of the front axle suspension and seat suspension tractor in seat pitch vibration acceleration change weak, show that the installation of seat suspension has no effect on the pitch vibration acceleration of seat; 2)compared with the front axle suspension tractor 3DOF vibration system, the installation of front axle suspension and seat suspension tractor seat vertical to the variation of vibration acceleration is very obvious, fell by an average of 61.1%, greatly improving the tractor driving comfort and safety of driving.