Maintenance of plunger type fuel injection pump for diesel engine
  • Automotive

According to the different conditions of the diesel engine, the fuel injection pump sends diesel oil to the injector regularly, quantitatively and steadily, and then injector diesel atomization into the cylinder. The failure of fuel injection pump directly affects the power, economy and environmental protection performance of tractor variant transporters. Therefore, timely and correct maintenance of fuel injection pump is very important. In the maintenance of the fuel injection pump, the main wear parts of the injection pump should be checked in order to make the decision of comprehensive disassembly and maintenance, so that the injection pump can achieve the original technical performance and ensure the normal work of the diesel engine. The matching parts between rack and fan in A and B pumps are important parts in the oil supply control mechanism. They are more closely matched and push and pull easily. It is difficult to reconstruct the gear surface by straightening method if the rack is found to be distorted or worn. If it is found that the push and pull card is stagnant and the stagnation position is changeable, it may be damaged on the tooth surface with foreign objects or individual teeth, and should be cleaned and repaired in maintenance and reassembled and retried. The clearance between the rack and the tooth surface, that is, the gap between the tooth surface and the tooth surface should not be more than 0.1 mm, and should be uniform in the working length. The push and pull force should not exceed 3 N. When the resistance is too large or when there is a stagnation, it should be cleaned and reassembled, and the new parts can not be replaced when it is not repaired. I pump oil quantity adjustment rack rod check. It is mainly to check the bending degree of the rod. The rack rod is bent because of the deformation of the pump body or under the stress of the rod. When more than 0.05 mm, the movement resistance of the pull rod is increased, the change of the oil supply characteristic curve of the oil pump is affected, the governor's adjustment function is invalid, and the cold pressure should be straightened or replaced. The function of the plunger coupling of the fuel injection pump is to increase the diesel pressure to satisfy the injection pressure requirement of the injector, and to control the oil quantity and the oil supply time. Plunger coupling is an important part of fuel injection pump assembly. It not only has good sealing performance, but also has good sliding property. If the stopper is dead or stuck, the rack movement will be difficult or even unable to move, and the regulator will fail. At this time, the engine will not start or work "lack of cylinder", unstable speed (high and low), self extinguishing or "flying". The pump oil of the plunger type fuel injection pump is completed by reciprocating movement of plungers in the plunger bushing. There are two small holes on both sides of the plunger sleeve, which are connected with the low pressure oil chamber on the fuel injection pump body. The oil valve couple is installed above the plunger coupling, and the oil valve spring is used to press the oil valve on the valve seat to form the oil pressure space with the plunger top. The lower end of the plunger is pressed on the tappet assembly by the plunger spring, and the tappet body is pressed on the cam on the camshaft through the roller. When the cams top up the tappet to make the plunger go up, the compressed diesel forces the oil valve to leave the seat and press into the nozzle through the high-pressure oil pipe into the nozzle and into the cylinder. After the plunger rises more than the effective stroke, the injection groove on the plunger connects to the lower edge of the plunger sleeve back to the oil hole, and the oil supply ends. The two sides of the A pump plunger double ears and the oil control sleeve are the movement control surfaces, which are one of the parts which are easy to wear. The standard fit clearance is 0.02 to 0.04 mm, and should be repaired if wear or pier width deformation exceeds 0.20 mm. When conditions permit, the two sides of the plunger and two ears can be thickened by local chromium plating to achieve standard fit clearance. The repairman can also use the hammering method to widen the ears and carefully grind them, so as to restore the original fit gap and replace the new parts when they are unable to repair. (1) the oil outlet valve is combined with the bread oil valve and the oil valve seat cone, the pressure relief ring of the oil outlet valve and the oil valve seat cylinder, and its matching face plays a sealing role, such as the serious wear and tear will lead to the decrease of the injection pressure. The oil outlet valve is not well sealed, and the grinding method can be eliminated. The oil valve is clamped on the drilling machine, coated with a little chromium oxide, oil or grinding ointment (not in the place that should not be grinded). It is grinded with the seat of the valve and should be cleaned and reloaded after the grinding. The surface of the grinding surface must have no groove marks and arcs, and the sealing is tight. (2) if the spring of the oil outlet valve is broken, twisted or weakened, it will reduce the oil pressure of the pump and the seating force of the spool of the oil outlet valve and need to be renewed. (3) dirt causes the oil valve to be tightly closed and should be cleaned after loading. (4) the oil outlet valve can not guarantee the residual oil pressure of the high pressure oil pipe, and it should be rubbed when affecting the startup and running performance of the engine. (5) high pressure oil seal copper gasket or low pressure oil seal rubber ring can not guarantee the sealing performance or damage, should be replaced. When assembling, the tightening torque of the joint should not be too large or too small. The tappet and the cylindrical surface of the tappet have the sliding and guiding function of the tappet column. The loose or stagnation will occur after the wear and tear, which will affect the oil movement of the pump plunger pump. The normal clearance should be 0.02 to 0.05 mm, and should be updated when the gap is too large. The overall clearance between the inner bush and the roller should be 0.01 to 0.04 mm. 5. cam and camshaft camshaft wear too large, will lead to plunger speed characteristic curve change, so that fuel injection rule changes. So when cam wear is serious, camshaft should be replaced. When the camshaft bearing is seriously worn, new bearings should be replaced to ensure normal operation of the camshaft. The causes of damage of cam and camshaft are as follows: (1) the axial clearance of the camshaft is too large, which causes the roller body to increase the impact force on the cam working face, thus aggravating the early wear of the cam surface. (2) the loosening of the tappet positioning screw leads to the deflection of the tappet. The roller deviates from the cam raceway, and the edges and corners of the tappet face contact with the surface of the cam, so that the surface of the cam is seriously scratched and worn. (3) II pump will cause a large number of diesel oil to leak into the fuel injection pump due to the wear and tear of the oil pump tappet and shell, and the damage of the sealing apron, resulting in deterioration of the oil. The camshaft aggravates the wear because of poor lubrication. (4) the quantity of oil in the fuel injection pump is not enough or the oil is too dirty. (5) the specifications of the plunger spring do not meet the requirements, and the elastic force is too large, so that the camshaft can be deformed and accelerated. (6) the quality of the camshaft itself is not good or the hardness of the cam surface does not meet the requirement when it is heat treated.

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