Research On A Little Shock And High Performance Two-way Brake Valve Of The Hydraulic Cylinder

In hydraulic system, hydraulic cylinder is an important hydraulic actuator of achieving the reciprocating linear motion. It is widely used in large-scale heavy-load hydraulic equipment. When the hydraulic cylinder is quickly braked,the oil path will be instantly cut off or changed direction, the buffer cavity of the hydraulic cylinder will generate a great impingement and vibration and noise under the influence of inertia of the moving parts.At present, internal buffering method and external braking way, for hydraulic cylinder, have high quality braking effect, but still exist some problems. Only when the hydraulic cylinder piston moves to the end of cylinder,the internal buffering method can be used to brake. The reversing valve braking of external braking way is just applicable to the low speed and light load hydraulic system. The overflow valve braking of external braking way has shock and oscillation for the overshoot of pressure. The effect of electro-hydraulic proportional valve braking is optimal, but electro-hydraulic proportional valve is very expensive and needs a demanding working environment and can′t achieve brake if the system without electricity. Specifically, when the high-speed andheavy-load hydraulic cylinder needs to brake at any position or because of the system suddenly without electricity, the shock and vibration and noise will be more serious. This situation will cause a great threat to the executive and control unit and pipeline, even lead to accidents, such as rollover accident.Aiming at this problem, the paper firstly studys the causation, damage and preventive measures of hydraulic shock. On the basis of a lot of the literature of hydraulic cylinder braking, the paper summarizes the strengths and weaknesses of existing hydraulic cylinder braking methods at home and abroad. And then,according to the features of basic hydraulic valves and the feedback control principle of load sensitive technology, a new kind of two-way brake valve of the hydraulic cylinder is designed. The brake valve, which combines the advantages of hydraulic change-over valve, shuttle valve, load sensitive throttle valve and so on, can achieve a continuous braking force to match the load inertia force and possesses the same braking effect in the two movement direction of hydraulic cylinder and also can achieve parking after brake.Under the given conditions. The brake valve, of which the detailed structures and 3-D models have been designed and the dynamic model of braking process has been built, has been indicated by MATLAB/Simulink dynamic simulation with fast and smooth braking to hydraulic cylinder and avoiding a great shock and vibration in the process of braking. The paper also analyzes the braking effect of the brake valve under different conditions or changing the structural parameters of the valve. Research shows that the brakevalve still can realize ideal brake in a wide range of load quality and initial velocity, and it has a strong ability to adapt to different conditions. The study also verifies the rationality of structural parameters of the brake valve by studying the braking effect of different equivalent diameter of orifice of load sensitive throttle valve core.At last, under the same working conditions with the two-way brake valve of the hydraulic cylinder, the paper simulates and analyzes the braking effect of pilot operated overflow valve by MATLAB/Simulink, and compares with the two-way brake valve of the hydraulic cylinder from pressure changes, braking time and braking distance. The results show that the two-way brake valve of the hydraulic cylinder has a smaller braking distance, a shorter braking time and the pressure of buffer chamber of hydraulic cylinder rising smooth. The braking property of the brake valve improves significantly,it is more able to meet the requirements of hydraulic brake.