The fuel injection pump is the most important component in the diesel fuel supply system. Its performance and quality have a great impact on the diesel engine. It is called the "heart" of the diesel engine. Its main function: to improve the diesel pressure, according to the engine's working order, load size, timing and quantitative delivery of high-pressure diesel to the injector, and the oil supply pressure of each cylinder is equal. Claim (1) The pump oil pressure should ensure the injection pressure and atomization quality. First, the pumping mechanism of the plunger pump The plunger and the plunger sleeve are a pair of precision coupling parts, which are not interchangeable after being paired and grounded, and require high precision and smoothness and good wear resistance, and the radial clearance is 0.002 to 0.003 mm. The cylindrical surface of the plunger head is cut with a chute, and communicates with the top through a radial hole and an axial hole, the purpose of which is to change the circulating oil supply; the plunger sleeve is provided with an inlet and an oil return hole, and is connected with the pump. The low-pressure oil chambers in the body are connected, and the plunger is placed in the upper body of the pump, and the positioning screws are used for positioning. The position of the chute head chute is different, and the method of changing the oil supply amount is also different. The oil discharge valve and the oil discharge valve seat are also a pair of precision couple parts, which can not be interchanged after pairing and grinding, and the matching clearance is 0.01. The oil discharge valve is a one-way valve. Under the action of spring pressure, the upper conical surface of the valve is closely matched with the valve seat. The function is to isolate the high pressure oil pipe from the upper end of the plunger when the supply is stopped, and prevent the oil in the high pressure oil pipe. Flow backward into the fuel injection pump. The lower part of the oil delivery valve has a cross section that can be guided and passed through diesel. There is a small cylindrical surface under the cone surface of the oil discharge valve, which is called the pressure relief belt. Its function is to quickly reduce the oil pressure in the high pressure oil pipe when the oil supply is finished, and avoid the oil drop phenomenon at the injection hole. When the ring is dropped into the valve seat, the upper volume is quickly increased, the pressure is rapidly reduced, and the spray is quickly stopped. Second, the main working principle of pump oil (1) During operation, under the action of the cam and the plunger spring on the camshaft of the fuel injection pump, the plunger is forced to reciprocate up and down to complete the pumping task. The pumping process can be divided into the following three stages.
(2) The amount of oil supplied should be in accordance with the exact quantity required for the operation of the diesel engine.
(3) Ensure that the oil is accurately supplied within the specified time according to the working order of the diesel engine.
(4) The oil supply and oil supply time can be adjusted positively, and the oil supply of each cylinder is ensured to be uniform.
(5) The oil supply law should ensure that the diesel combustion is complete.
(6) The oil supply starts and ends, the movement is quick, the oil is cut off simply, and the oil is dripped. Its main type: the fuel injection pump of the vehicle diesel engine can be divided into three types according to the working principle: the plunger type fuel injection pump, the fuel injection pump-injector and the rotor distributed injection pump.
(2) Oil inlet process: When the convex part of the cam rotates, the plunger moves downward under the action of the spring force, and the upper space of the plunger (called the pump oil chamber) generates a vacuum degree, when the upper end surface of the plunger After the oil inlet hole of the plunger sleeve is opened, the diesel oil filled in the oil passage 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 feed ends.
(3) Oil supply process: When the camshaft turns to the convex part of the cam to lift the roller body, the plunger spring is compressed, the plunger moves upward, the fuel is pressurized, and a part of the fuel flows back to the fuel pump through the oil hole. Cavity. When the top surface of the plunger covers the upper edge of the oil inlet hole of the sleeve, the pumping chamber at the top of the plunger becomes a sealing oil chamber due to the small clearance of the plunger and the sleeve (0.0015-0.0025 mm). Continue to rise, the oil pressure in the pump oil chamber rises rapidly, the pump oil pressure> the oil valve spring force + the high pressure oil pipe residual pressure, push the oil valve out, the high pressure diesel oil enters the high pressure oil pipe through the oil discharge valve, sprays through the fuel injector Into the combustion chamber.
(4) Oil return process: The plunger is supplied with oil upwards. When the chute (stop supply) on the plunger is connected to the oil return hole on the sleeve, the low pressure oil passage of the pump oil chamber and the plunger head The middle hole communicates with the radial hole and the chute, the oil pressure suddenly drops, and the oil discharge valve is quickly closed under the action of the spring force to stop the oil supply. After that, the plunger is still going up. When the convex portion of the cam is turned over, the plunger is further lowered by the action of the spring. The next cycle begins.
(5) Conclusion: Through the above discussion, the following conclusions are drawn: 1 The total stroke L of the plunger reciprocating motion is constant, determined by the lift of the cam.
2 The amount of oil supplied per cycle of the plunger depends on the oil supply stroke, and the oil supply stroke is variable regardless of the camshaft control.
3 The fuel supply start time does not change with the change of the oil supply stroke.
4 Turn the plunger to change the end of the oil supply and change the oil supply.