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traditional port control valve out of the oil through a valve to be, to listen to two ports in the valve opening corresponding to the relationship as early as the design process to determine when, in the course can not be modified, so that the oil through two the mouth of the flow or pressure can not be controlled independently of each other.

1, the traditional single-spool valve defects

conventional single spool valve hydraulic system consisting of a reasonable solution of the following features is difficult and the contradiction between the control:

(1) hydraulic system designed to improve system stability and reduce the impact of load changes on the speed, or sacrifice some of the functions we want to achieve, or additional hydraulic components, such as control valves, pressure control valve, by increasing the damping, stiffness to improve system speed improve system stability. However, this component will reduce the increase in efficiency, waste of energy; also makes the whole system can be * reduced, increasing costs.

(2) As for the special structure allows the user to achieve a particular function must purchase the corresponding hydraulic components, coupled with construction machinery manufacturers will be based on different end-user requirements to design the corresponding function, this will cause procurement of similar manufacturers, multi-standard hydraulic control components to meet the needs of the different functional requirements, the product is not conducive to universal and product management, will also greatly enhance the product cost.

(3) As the executive body and out of hydraulic fluid through a valve to control both sides of the pressure control actuator alone is impossible. Therefore, the oil pressure acting on the dorsal movement of the actuator opposite direction, with the dorsal oil pressure, the executing agency for the shelf-life movement, into the oil side of the pressure must be increased. This will make the function of the hydraulic system increases consumption, low efficiency, heat increases.

dual-spool hydraulic system technology, as the executing agency out of the oil side of the spool valve port location and control separate, independently of each other, so that by two different combinations of spool control, the use of software programming can be very good solution to the traditional single-valve system can not solve the problem, but also can be easily achieved in conventional hydraulic systems difficult to accomplish.

2, two-spool valve are two basic control strategies

due to two dual-port valve for control flexibility, the two ports can be taken separately flow control, pressure control or flow pressure control. Positive introduce two simple control strategy.

(1) load direction remains unchanged throughout the course of their work

We know, for cranes, excavators, loaders and other terms of the hydraulic cylinder in the direction of the whole course of their work load is always maintained. Following the example of the hydraulic cylinder luffing crane to explore the dual spool control strategies.

cylinder luffing crane in the course of its work force, the load remains the same direction, so we can take control of the hydraulic cylinder rod with a pressure control chamber with no flow control rod control strategy.

rodless cavity flow control is not connected to the rod by detecting the side of the valve chamber on both sides of pressure before and after, according to the required amount of flow into or out of, to calculate the size of valve opening; rod chamber side with pressure control , so that the side to maintain a low pressure, making more energy efficient.

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Since we use a non-pole cavity flow control, so the original control system available balance valve used in a pilot-operated check valve instead. This will eliminate system instability caused by balancing valve, thereby enhancing the system stability.

(2) load direction of the change in the course of their work

In this case, to take “into the oil side of the pressure control, the oil side of the flow control” in the hydraulic cylinder rod chamber side with pressure control, there is no flow control rod side chamber.

same direction as the load, due to the oil side of the flow control, we can two-way balancing valve with check valve to replace, thereby enhancing the stability of the system. Into the oil side with a pressure controller to maintain a lower reference pressure, on the one hand to improve system efficiency, the other hand, the system does not occur cavitation.
To make changes in the load direction

body of work can be well controlled, the other a PI controller will be applied to the rod chamber of the pressure controller, when the load direction changes, no rod chamber pressure will be reduced; If the rod will still maintain a low pressure chamber, when the load is large, the hydraulic cylinder will reverse direction. At this point we can use to monitor the increase in PI controller rodless chamber pressure changes, when the PI controller detects that the lever cavity pressure is lower than the reference value, will increase rod chamber pressure controller set pressure, thus ensuring the system works.