Handle the trip, the greater the corresponding secondary pilot pressure will lead to greater, controlled by the second pilot pressure of main valve core will lead to greater open degree, and the matching, the greater the opening of the main valve core, the main oil field points to the actuators, the more the faster the speed of executive element, the will, pass through negative pressure signal generator in the oil is less, the smaller the negative pressure signal of the pressure value will be; If handle travel is smaller, the corresponding secondary pilot pressure will be smaller, controlled by the second pilot pressure of main valve core opening will be smaller, and the matching, the smaller the opening of the main valve core, the main oil field points to the actuators is less, the speed of executive element will be slower, pass through negative pressure signal generator in the oil, the more the greater the pressure value will be negative pressure signal. Hydraulic pump according to the pressure value of the negative pressure signal to control its displacement, this is negative flow control.
Negative flow control is only suitable for variable pump, and flow detection device is added in common hydraulic multiway valve. Traditional hydraulic excavator negative flow control can simplify the form commonly, six hydraulic multi-way valve can be simplified as A, B, O three linkage variable throttle mouth, after careful analysis, found that negative flow control in essence is A kind of constant flow control, through the hydraulic multi-way valve bypass oil return path set on flow detecting element, control of the bypass oil return flow constant value for A smaller, thus reducing the bypass throttling loss and empty flow losses.
Negative flow control system also has A certain speed, the valve core is located in fine-tuning district, hydraulic multi-way valve port A, O mouth was in A state of open, make the pump output flow after P mouth is divided into two parts, one part through A mouth into the hydraulic cylinder, the other one by O throttling mouth back to the fuel tank and flow detection, in this process, the control through the flow for the fixed value O mouth, only need to adjust the valve core flow area of port A and O mouth, so that the pump output flow rate increase by A mouth into the hydraulic cylinder, so as to realize the speed regulation of hydraulic cylinder. The speed regulation characteristic of the system is similar to the ordinary valve, but the energy saving effect is better than the ordinary valve.
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