Core tip: the main structure and working principle of the plunger injection pump is explained: its main function is to improve the diesel pressure, according to the working order of the engine, the size of the load, the timing and quantity of the high pressure diesel oil to the injector, and the pressure of the oil supply in each cylinder is equal.
The fuel injection pump is the most important part of the diesel supply system. Its performance and quality have great influence on the diesel engine, and is called the "heart" of the diesel engine. Its main functions: to improve the pressure of diesel, according to the working order of the engine, the size of the load, to deliver the high pressure diesel fuel to the injector at a time and time, and the pressure of the oil supply in each cylinder is equal.
Requirement
(1) pump oil pressure must ensure the injection pressure and atomization quality.
(2) fuel supply should meet the exact quantity required for diesel engine work.
(3) ensure that the fuel supply is accurately provided within the prescribed time according to the working order of the diesel engine.
(4) oil supply and oil supply time can be adjusted, and ensure that all cylinders are supplied with oil evenly.
(5) the law of oil supply shall guarantee the complete combustion of diesel fuel.
(6) oil supply starts and ends, moves quickly, cuts off the oil to be crisp, avoids dripping the oil. Its main type: the fuel injection pump of vehicle diesel engine can be divided into three types: plunger injection pump, injection pump - injector and rotor distribution type injection pump, according to its working principle.
Pump oil mechanism for plunger pump
The plunger and plunger sleeve is a pair of precise pairs, which can not be interchanged after paired grinding. It requires high precision, smooth finish and good wear resistance. The radial clearance is 0.002 ~ 0.003mm. The cylinder of the plunger has a slant groove on the cylinder head, and through the radial hole, the axial hole and the top, the purpose is to change the circulation oil supply; the plunger sleeve has the inlet and the oil recovery holes, which are all connected with the low pressure oil chamber of the pump body. After the plunger suit enters the upper body of the pump, the positioning screw is used. The location of the plunger head chute is different, and the method of changing the fuel supply is also different. The oil outlet valve and the oil outlet valve seat are also a pair of precision couplings, which can not be exchanged after matching and grinding, and the matching clearance is 0.01. The oil outlet valve is a one-way valve. Under the effect of spring pressure, the conical surface of the upper part of the valve is closely matched with the seat. The function of the valve is to isolate the high pressure oil pipe from the upper end of the plunger in the stop supply, and prevent the oil in the high pressure oil pipe from pouring into the fuel injection pump. The lower part of the oil outlet valve is cross section, which can guide and pass through diesel fuel. There is a small cylindrical surface under the cone of the oil discharge valve, which is called the pressure relief ring. Its function is to reduce the oil pressure in the high-pressure oil pipe quickly when the oil supply ends, so as to avoid the phenomenon of oil dropping at the hole. When the belt falls into the valve seat, the volume of the upper part will increase rapidly, the pressure will decrease rapidly and the spray will stop quickly.
The main working principle of pump oil
(1) working, under the action of the cam and the plunger spring on the camshaft of the injection pump, the plunger is forced to move up and down, thus completing the pump oil task, and the pump oil process can be divided into three stages.
(2) the process of oil entering: when the convex part of the cam passes, the plunger moves downward under the action of the spring force. The upper space of the plunger (called the pump oil chamber) produces a vacuum. When the end face of the plunger opens the hole in the plunger sleeve, the diesel oil in the upper oil channel of the oil pump enters the pump chamber through the oil hole, and the plunger is transported by the plunger. Move to the bottom, and the oil is over.
(3) oil supply process: when the camshaft goes to the convex part of the cam to lift the roller body, the plunger spring is compressed, the plunger moves upward, the fuel is pressed, and a part of the fuel flows through the oil hole to the oil cavity of the oil pump. When the top surface of the plunger covers the upper edge of the oil hole, the pump oil chamber at the top of the plunger becomes a sealed oil chamber because the clearance gap between the plunger and the sleeve is very small (0.0015-0.0025mm), the plunger continues to rise, the oil pressure in the pump chamber rises rapidly, and the pump oil pressure > the spring force of the oil valve and the residual pressure of the high pressure tubing are pushed out. The oil valve, the high pressure diesel oil enters the high-pressure oil pipe through the oil outlet valve, and is injected into the combustion chamber through the injector.
(4) return oil process: the plunger upwards oil supply, when the slant slot on the plunger (stop supply) connects with the oil back hole on the sleeve, the low pressure oil circuit of the pump chamber communicates with the middle hole of the plunger head and the radial hole and the inclined slot, and the oil pressure drops suddenly, and the oil outlet valve closes rapidly under the effect of spring force and stops the oil supply. After that, the plunger must go up. When the convex part of the cam is turned over, the plunger will be down again under the action of the spring. Then the next cycle begins.
(5) conclusion: through the above discussion, the following conclusions can be drawn.
(1) the L of the reciprocating movement of the plunger is invariable, determined by the lift of the cam.
2. The amount of oil supplied to each piston depends on the oil supply stroke, and the oil supply stroke is not controlled by camshaft.
3. The beginning time of oil supply does not change with the change of oil supply stroke.
4. Turning the plunger can change the time of oil supply end, thus changing the fuel supply.
