Working principle of VICKERS plunger pump in the United States

Working principle of VICKERS plunger pump in the United States

Vickers plunger pump is a type of reciprocating pump, belonging to the volumetric pump. Its plunger is driven by the eccentric rotation of the pump shaft, reciprocating motion, and its suction and discharge valves are both one-way valves. When the plunger is pulled out, the pressure inside the working chamber decreases and the outlet valve closes. When the pressure is lower than the inlet pressure, the inlet valve opens and liquid enters; When the plunger is pushed inward, the working chamber pressure increases, the inlet valve closes, and when it is higher than the outlet pressure, the outlet valve opens and the liquid is discharged. The axial piston pump with sliding shoe structure is currently the most widely used axial piston pump. The plunger placed in the cylinder body contacts the inclined plate through the sliding shoe. When the transmission shaft drives the cylinder body to rotate, the inclined plate pulls out or pushes back the plunger from the cylinder body, completing the oil suction and discharge process. The oil in the working chamber composed of the plunger and cylinder bore is connected to the suction and discharge chambers of the pump through the oil distribution plate. The variable mechanism is used to change the inclination angle of the inclined plate, and the displacement of the pump can be changed by adjusting the inclination angle of the inclined plate.

Overview

The total stroke L of the reciprocating motion of the Vickers plunger pump is constant and determined by the lift of the cam. The fuel supply amount per cycle of the plunger depends on the fuel supply stroke, which is variable and not controlled by the camshaft. The start time of fuel supply does not change with the variation of fuel supply stroke. Rotating the plunger can change the end time of fuel supply, thereby altering the fuel supply amount. When the plunger pump is working, the cam on the camshaft of the fuel injection pump and the plunger spring force the plunger to reciprocate up and down, thereby completing the pumping task. The pumping process can be divided into the following three stages.

Oil inlet process

When the convex part of the cam rotates, under the action of the spring force, the plunger moves downward, and the upper space of the plunger (called the pump oil chamber) generates a vacuum degree. When the upper end face of the plunger opens the oil inlet hole on the plunger sleeve, diesel filled in the oil passage of the upper body of the oil pump enters the pump oil chamber through the oil hole, and the plunger moves to the bottom dead center, ending the oil inlet.

Oil supply process

When the camshaft rotates to the convex part of the cam and lifts the roller body, the plunger spring is compressed, the plunger moves upward, and the fuel is compressed. Part of the fuel flows back to the upper body oil chamber of the fuel injection pump through the oil hole. When the top surface of the plunger covers the upper edge of the oil inlet hole on the sleeve, due to the small clearance between the plunger and the sleeve (0.0015-0.0025mm), the pump oil chamber at the top of the plunger becomes a sealed oil chamber. As the plunger continues to rise, the oil pressure in the pump oil chamber rapidly increases. When the pump oil pressure is greater than the spring force of the outlet valve and the remaining pressure of the high-pressure oil pipe, the outlet valve is pushed open, and high-pressure diesel enters the high-pressure oil pipe through the outlet valve and is injected into the combustion chamber through the injector.

Return oil process

The plunger supplies oil upwards. When the inclined groove (stop supply edge) on the plunger is connected to the return hole on the sleeve, the low-pressure oil circuit in the pump chamber communicates with the middle hole, radial hole, and inclined groove of the plunger head. The oil pressure suddenly drops, and the oil outlet valve quickly closes under the action of the spring force, stopping the oil supply. Afterwards, the plunger will continue to move upwards. When the protruding part of the cam rotates past, under the action of the spring, the plunger will move downwards again. At this point, the next cycle begins.

A plunger pump is introduced based on the principle of a plunger. There are two one-way valves on a plunger pump, and the directions are opposite. When the plunger moves in one direction, negative pressure appears in the cylinder. At this time, one one-way valve opens and the liquid is sucked into the cylinder. When the plunger moves in the other direction, the liquid is compressed and the other one-way valve is opened, and the liquid sucked into the cylinder is discharged. This working mode forms continuous fuel supply after continuous movement.

Maintenance of plunger pump

Vickers inclined disc axial piston pumps generally adopt the form of cylinder rotation and end face flow distribution. There is a friction pair consisting of a bimetallic plate and a steel oil distribution plate embedded on the end face of the cylinder body, and most of them use a flat flow distribution method, so maintenance is relatively convenient. The oil distribution plate is one of the key components of an axial piston pump. When the pump is working, on the one hand, the high-pressure oil in the working chamber pushes the cylinder body towards the oil distribution plate, and on the other hand, the oil film pressure between the oil distribution plate and the cylinder body forms a hydraulic thrust on the cylinder body, causing it to deviate from the oil distribution plate. The hydraulic clamping force Fn of the cylinder body to the oil distribution plate is slightly greater than the hydraulic thrust Ff of the oil distribution plate to the cylinder body, that is, Fn/Ff=1.05-1.1, which enables the pump to work normally and maintain a high volumetric efficiency. In fact, due to oil contamination, there is often slight wear between the oil distribution plate and the cylinder block.

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Working principle of VICKERS plunger pump in the United States