Piston pumps at different stages

When working, under the action of the cam and plunger spring on the camshaft of the fuel injection pump, the plunger is forced to reciprocate up and down, and then the oil pumping task is completed, and the oil pumping process can be divided into the following three periods.
Oil intake process
When the bulge of the cam is turned some over, under the action of spring force, the plunger moves downward, and the upper space of the plunger (called the pump oil chamber) occurs in vacuum, when the upper end of the plunger turns over the oil inlet hole on the plunger sleeve, the diesel fuel that is covered in the oil duct 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, and the oil intake is completed.
Lubrication process
When the camshaft turns to the protrusion of the cam and jacks up the roller body, the plunger spring is tightened, the plunger moves upward, the fuel is pressurized, and some fuel flows back to the upper body oil cavity of the fuel injection pump through the oil hole. When the top surface of the plunger covers the upper edge of the sleeve traveling oil hole, because the cooperation gap between the plunger and the sleeve is small (0.0015-0.0025mm), the pump oil chamber at the top of the plunger becomes a sealed oil cavity, the plunger continues to rise, the oil pressure in the pump oil chamber increases, and the pump oil pressure >When the spring force of the oil outlet valve + the remaining pressure of the high-pressure oil pipe, the oil outlet valve is pushed open, and the high-pressure diesel enters the high-pressure oil pipe through the oil outlet valve and is sprayed into the combustion chamber through the fuel injector.
Oil return process
When the chute (stop supply side) on the plunger is connected with the oil return hole on the sleeve, the low-pressure oil circuit of the pump oil chamber communicates with the middle hole and radial hole and chute of the plunger head, the oil pressure drops suddenly, and the oil outlet valve is closed under the action of spring force, and the oil supply is continuous. After that, the plunger has to go up, and when the cam bulge is turned a little, the plunger goes down again under the action of the spring. Now the next cycle begins