Piontkevych O. Improving the efficiency of the multi-mode hydraulic drive of the front-end loader

The thesis is devoted to improving the efficiency of the hydraulic drive of the front-end loader boom, which reduces the energy losses in the hydraulic drive, as well as stabilizing the speed of its hydraulic cylinders and fixing the loaded boom in the working position with minimal leaks from the hydraulic cylinder chamber by developing a hydraulic drive based on the counterbalance valve. A non-linear mathematical model of an experimental sample of a boom hydraulic drive with the counterbalance valve has been developed. The simulation took into account the influence of the hydrodynamic force on the main spool of the counterbalance valve, the change in the amount of flow through its working window and the effect of the stochastic characteristics of the tensor of the moment of inertia of the executive body. A method for calculating the hydrodynamic force on the main spool based on the study of the working fluid flow in the counterbalance valve channels using the Autodesk Simulation CFD program has been developed. The calculation of the working fluid flow was performed by solving the three-dimensional Navier-Stokes equations, using the finite element method and the k-epsilon turbulence model. The non-linear mathematical model of the experimental sample of the boom hydraulic drive was solved in the MATLAB Simulink environment using the equal Rosenbrock method of the 2nd order. The influence of the parameters of the counterbalance valve on the location of zones of stable operation of the hydraulic drive is investigated. Optimized the parameters of the counterbalance valve by LP-search. The optimization criterion includes static, dynamic and energy characteristics of the hydraulic drive. An algorithm has been created for calculating the counterbalance valve for the selection of optimal design parameters that provide improved static, dynamic and energy characteristics of the hydraulic drive under operating conditions with counter and associated loads. The degree of tightness of a counterbalance valve, static and dynamic characteristics of an experimental sample of an hydraulic boom hydraulic drive are investigated. According to the results of the experiments, the degree of tightness of the counterbalance valve was determined at the level of foreign analogues. The error of stabilization of the flow does not exceed 8%. The absence of loss of working fluid through the servospool and the parabolic dependence of the speed of the servospool of the counterbalance valve on the load on the actuator are confirmed. With a probability of 95%, the adequacy of the developed mathematical model of an experimental sample of a hydraulic drive boom loader according to Fisher's criterion was confirmed. It is proposed to improve the scheme of the BOREX 2206 backhoe loader. In hydraulic scheme of the front-end loader the use of counterbalance valves instead of throttles with check valves reduces energy costs by 35% to perform the same operations at maximum feed. Transients during braking or overcoming obstacles front-end loader are stable, and the transition process does not exceed 1.3 seconds.