The suction and pressure of the fuel injection pump are completed by the reciprocating motion of the plunger in the plunger sleeve. When the plunger is located in the lower position, the two oil holes on the plunger sleeve are opened, and the plunger sleeve cavity is communicated with the oil passage in the pump body, and the fuel quickly fills the oil chamber.
When the CAM pushes up against the roller of the roller body, the plunger is raised. Move upward from the beginning of the plunger until the oil hole is blocked by the upper end face of the plunger. During this time, due to the plunger’s movement, fuel is forced out of the oil chamber and into the oil passage. So this lift is called prestroke. When the plunger blocks the oil hole, the oil pressing process begins. The plunger goes up, and the oil pressure in the oil chamber rises sharply. When the pressure exceeds the spring elasticity of the oil outlet valve and the upper oil pressure, the top out of the oil valve, the fuel is pressed into the tubing and sent to the injector.
The time when the oil inlet hole on the plunger sleeve is completely blocked by the upper end face of the plunger is called the theoretical oil supply starting point.
When the plunger continues to move upward, the oil supply continues, and the oil pressure process continues until the screw bevel on the plunger sleeve opens the oil hole. When the oil hole is opened, the high pressure oil flows back to the oil channel in the pump body from the oil chamber through the longitudinal groove on the plunger sleeve and the oil return hole on the plunger sleeve. At this time, the oil pressure of the plunger sleeve oil chamber decreases rapidly, the oil outlet valve falls back to the valve seat under the action of the oil pressure in the spring and high pressure tubing, and the injector stops oil injection immediately. At this point, although the plunger continues to rise, the oil supply is terminated.
The moment when the oil return hole of the plunger sleeve is opened by the hypotenuse of the plunger is called the theoretical oil supply end point.
From the above oil absorption and oil pressing process, in the whole process of upward movement of the plunger, only the middle part of the stroke is the oil pressing process, this stroke is called the effective stroke of the plunger.
Post time: Jan-13-2023