| A hydraulic transmission technology is being developed rapidly in the field of mechanical transmission.A hydraulic cylinder as one of the executive components of a hydraulic system can convert pressure from a hydraulic working medium into the mechanical energy,and realize the reciprocating linear motion of mechanical parts.When the hydraulic cylinder in work needs to be stopped at any positions of its working range,the load and the inertia force of the piston will cause the hydraulic impact.The impact of the hydraulic system is often accompanied by vibrations and noises,which has an obvious influence on the system to work normally,in addition,the severe hydraulic impact will destroy the hydraulic press,even triggering the mechanical accident.Therefore,studying and improving the hydraulic cylinder braking processes and forms is of great significance for buffering and braking of the hydraulic cylinder.The current buffer braking methods used in hydraulic cylinders are mainly divided into two ways: inside cylinder buffer brake and outside cylinder buffer brake.There are some limitations in the inside buffering brake mode for hydraulic cylinder,in which the buffer process is only appear at the end of the hydraulic cylinder,but can not make brake of the hydraulic cylinder in any row positions.The way of outside buffer brake for hydraulic cylinder often by the function of the auxiliary components,such as the control element like of the overflow valve or the accumulator to realize the buffering brake at any position of hydraulic cylinder in braking process.But this application range is limited to the situation where the load is not heavy and the running speed of the hydraulic cylinder is low.Aiming at the buffering and braking measures of hydraulic cylinder under high speed and heavy load,this paper proposes a new buffer brake structure and a relevant hydraulic circuit.Firstly,the author studies and summarizes same hydraulic impact phenomenon,and makes some references to many research results domestic and abroad about buffer braking modes of hydraulic cylinder.At the same time,we combined with the load sensitive technology and the existing hydraulic control components,put forward a new load sensitive brake valve loop of the hydraulic cylinder.When the brake valve circuit breaks down suddenly or needs the hydraulic cylinder to stop running at any positions,the hydraulic cylinder can be quickly and smoothly braked.Besides,the braking effect is the same in the two working directions of the hydraulic cylinder,the whole hydraulic system structure is simplified.In addition,when the process is finished,the outside cylinder buffer circuit can lock the hydraulic cylinder to move freely,ensure the safety and stability of the hydraulic system.After that,the whole structure of the load sensitive brake valve is expounded and designed.The structure of the brake valve is chosen according to the specific working condition parameters,and the structure of the load sensitive brake valve choice the internal integrated valve.The hydraulic components which constitute the brake valve are designed and selected.The rest of the hydraulic pressure valve and the hydraulic reversing valve are used the existing types of products.The valve is designed and built by three-dimensional model with mainly designed and calculated the spool structure of the load sensing valve.After confirming the structure of the brake valve,we deduce the mathematical model of the working environment of the valve,and use MATLAB/Simulink to build the simulation model.Through the analysis of the simulation results,the load sensitive brake valve can complete the hydraulic cylinder buffer brake in a short time.There is no serious hydraulic impact in the whole buffer process,and the buffer effect is fine.In order to verify the practicability of the designed brake valve,the MATLAB/Simulink is used to simulate and analyze the braking effect of the brake valve under the conditions of different working parameters.The simulation results show that the buffer effect of the load sensitive brake valve to the hydraulic cylinder is still well after the change of the load quality and the initial velocity of the piston in a certain range.The overall structure of the system is reasonable and can meet the requirements of the buffer braking under different working conditions. |
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