How to distinguish the axial and radial directions of the plunger pump of a single-column hydraulic press. But regardless of the axial or radial direction, the pressure-compensated variable pump is automatically controlled by the pressure of the pump itself. The displacement of the axial pump can be controlled by simply adjusting the angle of the swash plate. At the same time, the compression of the spring is adjusted to change the unloading pressure of the pump. The radial pump can change the displacement by adjusting the eccentricity "e". The eccentricity can be adjusted manually or automatically by pressure. The principle is to open the spring to achieve unloading.
Constant pressure variable pump: When the output pressure is less than the set constant pressure, the full displacement of hydraulic oil is output, that is, quantitative output. When the output oil pressure reaches the set pressure, the displacement of the pump will be automatically adjusted to maintain constant pressure.
The main part (see structural section) is driven by the transmission shaft to rotate the cylinder, causing the seven plungers evenly distributed on the cylinder to rotate around the center line of the transmission shaft, and the sliding shoes in the column slide assembly are pressed against the variable head ( or swash plate). In this way, the plunger reciprocates with the rotation of the cylinder to complete the oil suction and oil pressing actions.
The outlet flow rate of the pressure-compensated variable pump changes approximately according to the constant power curve within a certain range with the outlet pressure. When the high-pressure oil from the main body enters the lower chamber (d) of the variable housing through channels (a), (b), and (c), the oil enters channels (f) and (h) respectively through channel (e). When When the force of the spring is greater than the hydraulic thrust entering the annular area at the lower end of the servo piston from the oil passage (f), the oil passes through (h) to the upper chamber (g), pushing the variable piston downward to increase the flow rate of the pump. When the hydraulic thrust acting on the annular area at the lower end of the servo piston is greater than the force of the spring, the servo piston moves upward, blocking the channel (h), allowing the oil in the (g) chamber to pass through the (i) chamber to relieve pressure. At this time, The variable piston moves upward and the variable head deflection angle decreases, causing the pump flow rate to decrease.
When adjusting the flow characteristics, you can first screw the limit screw to the upper end, adjust the spring sleeve according to the required flow and pressure change range, so that the initial pressure when the flow begins to change meets the requirements, and then screw the limit screw to the end. The flow rate at the stage pressure will no longer change, and the relationship between flow rate and pressure change is determined by the design of the pump itself.
