Fuel injection pump is the diesel fuel supply system, the most important piece, its performance and quality of diesel great influence, known as the "heart" of the diesel engine. one. Function, requirement, type Function: Raise the diesel pressure, according to the working sequence of the engine, the load size, timing and quantitative delivery of high pressure diesel fuel injector, and the cylinder pressure equal. Requirements: (1) pump oil pressure to ensure the injection pressure and atomization quality requirements. (2) The amount of fuel supply should be consistent with the exact number of diesel engine work required. (3) Ensure that the diesel engine work order, accurate supply of oil within the prescribed time. (4) adjustable fuel supply and fuel supply time, and ensure uniform fuel supply to each cylinder. (5) The law of fuel supply should ensure that diesel combustion completely. (6) start and end of fuel supply, agile, off the oil simply to avoid dripping. Type: Automotive diesel injection pump according to their working principle can be divided into plunger-type injection pump, injection pump - injector and rotor dispensing pump three categories. two. Piston pump oil pump principle Piston pump pump oil mechanism consists of two sets of precision couplings: Plunger and plunger sleeve is a pair of precision couplings, after the pair can not be exchanged for grinding, requiring high precision and finish and Good wear resistance, the radial clearance of 0.002 ~ 0.003mm Cylindrical head of the plunger cut a chute, and through the radial hole, the axial hole and the top of the same, the purpose is to change the cycle of fuel supply; column Plug on the system into the back to the oil hole, are connected to the pump on the body low-pressure oil chamber, the plunger set into the pump body, the positioning screw positioning. Plunger head chute location, change the amount of fuel supply is also different. Outlet valve and the valve seat is also a pair of precision couplings, can not be swapped after grinding, with the gap of 0.01. Outlet valve is a one-way valve, under the action of spring pressure, the upper conical surface of the valve is tightly matched with the valve seat. Its function is to cut off the high pressure oil pipe from the upper cavity of the plunger to prevent the oil in the high pressure pipe Inverted into the injection pump. The lower part of the oil valve is cross-section, both to guide, but also through the diesel. Under the conical surface of the valve, there is a small cylindrical surface, called the vacuum ring, whose function is to quickly reduce the pressure of oil in the high-pressure tubing when the fuel supply ends, so as to avoid dripping oil at the orifice. When the ring falls into the valve seat, the upper volume increases rapidly, the pressure decreases rapidly, and the injection is stopped rapidly. Pump oil principle work, the cam and plunger spring on the camshaft of the fuel injection pump, forcing the plunger up and down reciprocating motion, thus completing the pump oil task, pump oil process can be divided into the following three stages. Into the oil process when the convex part of the cam turn, under the action of the spring force, the plunger moves downward, the upper space of the plunger (called pump oil chamber) to produce a vacuum, when the plunger on the end face of the plunger sleeve After the oil inlet hole is opened, the diesel fuel filled in the upper body oil passage of the oil pump enters the oil pump chamber through the oil hole, and the plunger moves to the bottom dead center, and the oil enters the end. Oil supply process When the cam shaft to the raised part of the cam lift the roller body, the plunger spring is compressed, the plunger upward movement, the fuel pressure, part of the fuel flow through the hole back to the fuel injection body oil chamber. When the plunger top cover the upper edge of the sleeve into the oil hole, due to the small clearance between the plunger and sleeve (0.0015-0.0025mm) so that the top of the plunger pump chamber becomes a sealed oil chamber, the plunger Continue to rise, the pump oil chamber pressure rapidly increased, pump oil pressure> spring force of the valve + high pressure tubing remaining pressure, open the valve, high pressure diesel oil into the high pressure tubing through the injector spray Into the combustion chamber. Oil return process up the plunger, when up to the plunger on the chute (stop for the side) and the sleeve on the return hole, the pump chamber low pressure oil and the plunger head of the hole and the hole Radial hole and chute communication, a sudden drop in oil pressure, the oil valve in the spring force quickly shut down, stop the fuel supply. After the plunger has to go up, when the convex part of the cam turn, under the action of the spring, the plunger down again. At this point they started the next cycle. Conclusion: From the above discussion, the following conclusions can be drawn: â‘ The total stroke L of plunger reciprocation is constant and depends on the lift of the cam. (2) The amount of fuel supplied by the plunger per cycle depends on the fuel supply stroke, and the fuel supply stroke is variable regardless of the camshaft control. â‘¢ fuel supply start time does not change with the change of fuel stroke. â‘£ Turn the plunger can change the fuel supply end time, thus changing the fuel supply.
