As the name suggests, the variable piston pump is a piston pump whose output flow can be automatically adjusted according to the pressure change of the system (the size of the external load). The advantage of the variable piston pump is that it can automatically adjust the flow rate. When the pressure is high, the output flow rate is small, and when the pressure is low, the output flow rate is large. This can save the number of hydraulic components, simplify the oil system, and reduce oil heating.

Variable plunger pump types:

There are many types of variable piston pumps on the market. According to different application scenarios and different performance requirements, the variable piston pumps selected are different. Here are some common ones:

1. Axial variable piston pump:

2. Constant pressure variable plunger pump;

3. Automatic variable plunger pump;

4. Inclined axis variable piston pump;

5. Manual variable plunger pump;

6. High pressure variable plunger pump;

7. Constant power variable plunger pump;

8. Rated variable plunger pump;

9. Bidirectional variable plunger pump, etc.

Variable piston pump model:

The general expression method for the model of a variable piston pump is: nominal displacement - variable form (with motorized servo variable, pressure compensation variable, electric variable, manual variable, etc.) - pressure level - Y (pump) or M (motor) - 14-1 (first structure code) - technical improvement code (A, B, C, etc.) - no mark or F (no mark means forward rotation direction, F means reverse rotation direction).

Variable plunger pump parameters:

(1) Pressure: including working pressure and rated pressure. Working pressure refers to the output pressure of the pump, and its value is determined by the external load. Rated pressure refers to the highest pressure recommended for continuous use based on experimental results. It reflects the capacity of the pump (generally the pressure marked on the pump nameplate).

(2) Displacement: refers to the volume of oil that can be discharged by a plunger pump in one revolution without leakage, including theoretical flow and actual flow. The ratio of the actual flow to the theoretical flow of the pump is called volumetric efficiency.

(3) Power: includes input power and output power. Input power is the mechanical power to drive the hydraulic pump, and output power is the hydraulic power output by the plunger pump.

Variable piston pump structure:

Variable piston pump, including rear pump body, front pump body and main shaft. Among them, the rear pump body is composed of a first variable housing, a variable shaft, a variable spring, a second variable housing, an adjusting bolt, a spring adjusting rod, a variable spring seat, a valve seat, a swash plate, a variable pin, a sliding shoe, and a return plate; the front pump body is fixedly installed with bearings; the main shaft includes a cylinder block, a distribution plate, a plunger sleeve, a plunger, a valve body, a spring sleeve, a spring jacket, a control piston spring, and other structures.

Working principle of variable plunger pump:

The pressure oil of the variable plunger pump enters the lower chamber of the variable housing through the pump body and the oil passage hole in the variable housing of the pump housing through the one-way valve. When the pull rod moves downward, the servo piston is pushed to move downward, the upper valve port of the servo valve opens, and the pressure oil in the lower chamber of the variable housing passes through the variable housing. The oil passage hole in the measuring piston enters the upper chamber of the variable housing. Since the area of the upper chamber is larger than the lower chamber, the hydraulic force pushes the piston downward, driving the pin to rotate the variable head around the center of the steel ball, changing the inclination angle of the variable head (increasing), and the flow rate of the plunger pump increases accordingly. On the contrary, the pull rod moves upward, the inclination angle of the variable head changes in the opposite direction, and the flow rate of the pump also changes accordingly. When the inclination angle changes to zero, the variable head changes to the direction of the negative deflection angle, the liquid flow is reversed, and the inlet and outlet of the pump change.

Variable piston pump applications:

Variable piston pumps are now widely used in situations where high pressure, large flow and flow need to be adjusted, such as hydraulic presses, engineering machinery, ships and other fields. The specific application scenarios are as follows:

● Excavator

● Concrete mixer truck

● Concrete pump truck

●Pumping station

●Paver

● Crane

● Hydraulic winch

● Rolling mill

● Injection molding machine

● Petroleum equipment

● Environmental protection and other hydraulic machinery