The impact of the accuracy class of bearings, rotational speed, load, clearances, and fits on the vibration levels of electric motor bearing units is investigated. The ways to reduce the vibrations of mechanical origin are offered. The boundary vibration levels of asynchronous motors limited by vibration levels of 40 dB at a frequency of 5 Hz and 80 dB at a frequency of 10,000 Hz are determined. The effect of increasing the rotational speed and load on the vibration levels of bearing units has been determined, and reserves for reducing vibration while ensuring the optimum bearing preload on the shaft journal have been identified. It is established that the clearance between the cap and the bearing when it is fixed in the housing (primer) does not ensure the unambiguity of the bearing unit assembly, which results in a large variation in vibration levels compared with rigid and elastic fixation. The results of this research can be applied to all types of traction electric motors.
Wheel-type tractors carry out a range of processing operations, with the exception of early spring work, when caterpillar tractors are used to reduce the compaction effect on the soil. Therefore, to plan the costs and reserves associated with fuel consumption, it is necessary to have an estimate of the fuel economy of the tractor in basic agricultural operations. An objective assessment of fuel consumption requires a mathematical model that describes the fuel characteristics of the engine, taking into account the speed and load torque in a wide range of variation. Verification of the model is possible only with experimental data. Since the efficiency and fuel economy of a tractor depends not only on engine performance, but also on the perfection of the transmission, the running system and the rational choice of speed, it is necessary to take into account the time-varying nature of the tractor’s traction load. The complex of agricultural operations can be divided into characteristic cycles of load change over time. This principle is the basis of PowerMix test cycles, which are conducted on a concrete track to ensure repeatability of the experiment. The use of the variable load on the tractor in the PowerMix tests is positive, but in actual field tests the results may differ due to the instability of the soil properties. On the other hand, PowerMix field cycles can be taken as standard test loads in the simulation of tractor traction tests on the ground
The results of research on the creation of induction traction electric motors (EM), which made it possible to improve their technical, environmental and operational qualities, are presented. The main criterion for assessing the quality of EM were selected vibration levels. The main research methods were experimental and statistical methods. New technologies for assembling bearing units assemblies and EM as a whole were studied. New design and technological solutions have been developed. The dynamic characteristics of structural vibration damping have been improved by methods of rational distribution of masses, stiffness and distance between supports of bearings. The achieved reduction in vibration levels makes it possible to predict an increase in the resource developed by the EМ by 2-3 times.
Purpose of the study is to develop a matrix method for studying the dynamics of a tractor as a multi-mass spatial system of rigid bodies with an arbitrary arrangement of elastic suspension of bodies on shock absorbers relative to a fixed support surface and the presence of elastic connections between the bodies, made in the form of beam elements. Research methods. The methodological basis of the work is the generalization and analysis of well-known scientific results regarding the dynamics of two-mass systems in resonance modes and the use of a systematic approach. The analytical method and comparative analysis were used to form a scientific problem, determine the goal and formulate the research objectives. When creating empirical models, the main provisions of the theory of stability of systems, methodology of systems analysis and research of operations were used. The results of the study. A wheeled vehicle is presented as an amortized continuous frame type structure with assemblies and assembly units located on it, as well as a methodology for calculating individual block matrices of stiffness and damping coefficients. In this case, it is assumed that a viscous damper can be connected in parallel to each elastic element. In this construction of the stiffness and damping matrix of the block matrix are formed in the same way. Damping matrices are derived from the corresponding matrices by substituting damping constants instead of stiffness constants. To determine the natural frequencies and vibration modes of an undamped system using a PC, the most effective method of diagonalization by successive rotations. This method provides a complete solution to the problem, allowing all frequencies and shapes to be determined simultaneously, and good convergence. Conclusions. The considered method for analyzing and calculating the dynamics and vibration damping of a tractor as a complex mechanical system is based on a matrix record of the problem of spatial vibrations of a system of rigid bodies with elastic bonds. Matrix equations seem to be especially useful in the study of complex tightly coupled systems with the obligatory use of a PC. The presented work provides a complete methodology for calculating a tractor as a complex mechanical system such as a spatial frame with equipment installed on it.
During rectilinear motion of a wheeled tractor on a deformable surface, its rear wheels move along the track formed by the front ones. The amount of soil compaction can be different depending on its physical and mechanical properties, the dimensions of the front wheels of the tractor, the weight load falling on the front axle, and the like. Accordingly, the traction abilities of the rear drive wheels will also be different. This circumstance should be taken into account when designing wheeled tractors, especially tractor-tractors with two driving axles, in which a change in any of the factors listed above, for example, the distribution of the load along the axles, affects not only the compaction of the surface on which the rear wheels move, but and on the traction qualities of the front. In the course of the research, it was found that with a decrease in the load distribution coefficient below 0.5, the role of the rear wheel, which is capable of developing a greater traction force than the front wheel at the same load, in the formation of the total traction force, decreases. Therefore, the total traction force of the driving wheels becomes lower. With an increase in this coefficient above 0.5, the amount of preliminary soil compaction by the front wheel decreases; as a result, the ability of the rear wheel to develop more traction than the front wheel under the same load is reduced. The greatest traction force of two driving wheels moving along the same track is achieved with the same weight loads. Thus, the position of the center of gravity of a tractor with four driving wheels of the same size should be chosen in such a way that the load on the front and rear wheels is equalized at the rated pull on the hook. When conducting research on a field prepared for sowing, with an active semi-trailer with different load distribution between the rear axle of the tractor and the axle of the semi-trailer, it was found that the center of gravity of the active semi-trailer can be selected in the same way as for the inactive one, i.e. taking into account the influence of the semi-trailer on traction performance. The dependences obtained in the work make it possible to analyze the traction qualities of several driving wheels when they roll along one track. With their help, it is possible to identify the effect of surface compaction on the traction qualities of the rear moving front wheels; the influence of load distribution along the axles of the driving wheels on their total traction force, etc.
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