Used to control the hydraulic drive in the direction of flow and pressure, the liquid components. Control the pressure and flow control valves as pressure called flow control valves, control, and the general direction of flow control valve is called. Pressure relief valve control according to the purposes into valve, valve and order. (1) the relief valve: can control hydraulic system set in when the constant pressure. The relief valve for overload protection called valve. When the system pressure to malfunction, may cause damage when the allowable value, the mouth will open and overflow, in order to ensure the security of the system. (2) valve: can control circuits are main branch of hydraulic circuits of low pressure. According to its control valve, and pressure can be divided into different functional value output pressure relief valve (for a constant value), set the input and output pressure differential pressure (of) and valve (than the input and output pressure to keep certain proportion. (3) order valve: can make a actuators (such as hydraulic cylinder, hydraulic motor, etc.), sequential action to other components of action. The pressure pump hydraulic cylinders to push through sports, 1 order JinYou valve in area A mouth, when the hydraulic cylinder 1 movement after completely, pressure, the effect of upward pressure on A set of values greater than spring after A rise JinYou valve core, with A mouth to mouth, make oil hydraulic cylinders and movement.
The flow control valves and valve core using the area between the throttle and its local resistance to flow, and the implementation of components of the control speed. According to the purposes is divided into five flow control. (1) the throttle: in the area after adjustment for throttling, can make the load stress and uniformity of big changes require actuators velocity basically stable. (2) control valves in load pressure changes, can maintain the throttle to the pressure.all value. So, in the area after adjustment for throttling, no matter how changes in speed, load pressure by the throttle valve can keep constant, so that the flow velocity stability of the actuator. (3) : no matter the purge valve size, can make the same load oil source of two components for the amount of traffic get equal the purge valve or synchronous valve, Get in proportion to the purge valve proportion of flow. (4) collecting the purge valve disc: and that, on the contrary, the flow into collector valve proportional distribution. (5) collecting the purge valve and concurrently valve: collecting valves two functions.
Direction control according to the purposes into fitting and reversing valves. Check: only allows fluid in pipe line, one-way cut backward. Reversing valves: change between the different pipeline, broken relationship, according to the work in the body of valve core position number two, three points; According to the number of channel control clinic, three, four points, five; etc. According to the valve spool driver broke, motor, fixed mode of electric, hydraulic, etc. Figure 2 for three directional control valve spool principle of work. P for fuel oil, O for A mouth, and B is to export the actuators. When the valve is in full in the mouth, oil, actuators. When the valve is moved to the right position, P and A general, B and O, When the valve is moved, P and left, A and B O. So, can make positive, backward motion.
In the late 1960s, hydraulic control valves are the basis and developed electrohydraulic proportional valves. Its output (pressure, flow rate of the input signals can) with continuous change. Electrohydraulic proportional control effect by different, accordingly into electrohydraulic proportional pressure valves, electro-hydraulic proportional valve and electrohydraulic proportional direction control valves, etc.
