| Hydraulic counterbalance valve is a sort of important elements in the hydraulic balanced loop, which is widely used in modern engineering mechanism field, especially elevating machinery. The counterbalance valve is usually applied to control descending rate of the load in order to prevent dangerous because of speeding when the load drop. But the traditional counterbalance valves have many pieces of disadvantage: it easily appears low frequency vibration when the load is very heavy, which will lead stationarity of work not to be guaranteed and have a bad safety; the control pressure will high when the load is very light, which will make the system power serious damage. Aiming at the disadvantage above, a new sort of the load-sensing counterbalance valve (it has been declared patent of invention and the public number of patent is CN1945028) is researched in the literature [1]. Compared with the common valve, which the open amount is large when the load is heavier, and the open amount is large when the load is lighter. However, the open amount of this valve will reduce as the load increase. It makes the load decline steady and let the control pressure remain basically unchanged, thus ensuring the power loss is smaller as small load. The load-sensing theory is applied in this designing, which the pressure signal from the lower cavity of hydraulic cylinder is fed back to the valve to make the size of valve plug uncork change according to the load change in order to solve the exiting problem that the backpressure can't change with the load pressure thoroughly. In this paper, the theory of load-sensing counterbalance valve is elaborated deeply. Its structure is detailed and especially, its key parts are computed and designed in detail. The regulation performance and control performance of the valve are ameliorated hugely through design calculation of small holes on valve core, and the structure of the entire counterbalance valve is more compact and the design is more reasonable so as to meet the performance requirements.The mathematical model of this new counterbalance valve is established, and the computer simulation on dynamic characteristics is carried on by the software MATLAB/Simulink. Optimization of some parameters is achieved by calling MATLAB optimization function statement In the Simulink module. It confirmed that compared to other counterbalance valve products (such as literature [2]: at light load 1.5s and heavy load 2.1s), this valve are markedly improved in the steady-state area.In view of the force equilibrium of valve core, the actual area and the theory area of throttling port is much closer after small holes on valve core being redesigned. In the process of redesigning throttle valve core, according to the design parameters of the load-sensing counterbalance valve, the flow field inside the spool valve during spool moving was simulated and analyzed. Three- dimensional geometric model of throttle valve core in counterbalance valve is established by using Pro/E software and the division of the grid is carried by using pre-processing software Gambit. In a given four kinds of pressure and the corresponding four kinds opening amount of valve core, flow state of fluid in fluid channel of throttle valve and the emergence of vortex region are simulated by using standard turbulent flow model, and through the average speed of each small holes on valve core is intercepted, thereby flow stability is verified. The conclusion provides a reference for the structural design and optimization of valve core.Finally, the drawings of this balance valve are drawn and it is processed. Combined with the characteristics of the balance valve, an experimental analysis is conducted and experimental scheme is given. It established a foundation for further confirming that the overall performance of this new counterbalance valve has been improved markedly comparing with the old one.
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