Rexroth variable piston pump displacement control mode

1. Guiding ideology:

1. The pressure depends on the load oil pump, and the output pressure is inversely proportional to the flow rate. In the state of electronic control, when the external load increases, the system pressure increases, when the system pressure increases, the pressure of the front pump oil flow and the rear pump oil flow into the rear pump increases, and the pilot secondary pressure of the electro-proportional valve outlet is also greater by the computer detection relevant signal, the former acts on the primary piston, the latter acts on the secondary piston, and the two push the piston to overcome the spring force to move to the left, and the piston pushes the spool of the spool to the left to overcome the spring force of the spool to move to the left, so that the spool of the spool is in the left position.

2. At this time, the oil flow of the rear AY oil pump can act on the large end of the variable piston through the left position of the spool of the spool of the slide valve, where the oil passage changes from normally closed to normally open, because the cross-sectional area of the two ends of the piston is unequal, the pressure acting on the large end of the variable piston of the swash plate is greater than the pressure at the small end of the variable piston plunger, and the plunger moves to the left.

3. At the same time, the position change of the swash plate and the spool valve sleeve: the swing angle of the swash plate gradually decreases, which reduces the displacement of the oil pump, and the sliding sleeve of the spool valve moves to the left at the same time, and gradually cuts off the oil passage communicated between the variable piston cavity and the oil flow of the rear pump, when the oil port is completely cut off, the swash plate is stationary, the swash plate no longer swings, the oil pump completes the variable, and the flow output is stable.

2. When the external load becomes smaller, the system pressure becomes smaller, the three oil flow pressures acting on the first and second stage pistons become smaller, the balance between the oil flow pressure and the spring force is broken, the spring is gradually pushed back, and the spool of the spool is gradually pushed back to the right, so that the large cavity oil channel of the inclined plate piston is communicated with the oil drain port, and the pressure of the large cavity of the variable piston begins to be reduced.

3. At the same time, the swash plate and the spool valve sleeve are changed: the angle of the swash plate gradually increases, and the displacement of the oil pump is increased; At the same time, the sliding sleeve of the slide valve moves to the right, and gradually closes the oil channel between the large cavity of the swash plate and the oil drain port, when the spring force and the oil flow pressure form a new balance and the oil channel between the piston cavity and the oil drain port is completely cut off, the plunger no longer moves, the swash plate no longer swings, the oil pump completes the variable, and the flow output is stable. When the external load changes, the balance between the oil flow pressure and the spring force is broken again, and the displacement also changes, and the two always change with the change of load, in a dynamic balance.

Four. Electronic control state: The control hydraulic signal related to the displacement change is the oil flow of the front pump, the oil flow of the rear pump and the pilot oil and negative flow, in which the oil flow of the front and rear pumps directly controls the oil pump, and the pilot oil controls the oil pump after throttling through the electric proportional valve, which we can call the pilot secondary pressure. Let's take the control of the pump as an example to analyze the change in displacement.

Rexroth variable piston pump displacement control mode

Rexroth variable piston pump displacement control mode

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