Plunger steam injection pump: operating requirements, types of faults and operating principle

Recently, more and more people have started using diesel cars. And for that there are reasons. So, this is a high compression ratio, low fuel consumption, good traction at low revs. One of the main components of the fuel system of a diesel engine is a pump. Its design includes a plunger steam injection pump. What is this detail and what is it for? Let's talk about this in our today's article.

Characteristic

At the heart of the high-pressure fuel pump is a special pump section. It includes a plunger (piston) and a cylinder having the shape of a small bushing. This pair of parts is made of high-strength steels, because it works under high pressure. The plunger pair of the injection pump performs the function of creating the fuel pressure necessary to further atomize it in the combustion chamber. Note that this mechanism is highly accurate. The main characteristic that the plunger pair of the injection pump (Zexel including) possesses is the exact dosage of fuel and the regulation of its pressure.

Device

This assembly consists of two grooves:

• Spiral.
• Longitudinal.

The pair itself includes 4 sleeves and 5 plungers. In the first there are 2 channels - bypass and supply. Both are connected to each other with a combustion chamber. Above the plunger pair is a fitting with a landing cone.

Due to the high precision of the inner cylinder treatment, the plunger steam of the injection pump can work under pressure up to 200 MPa. The characteristics of such pumps at times exceed the performance of conventional piston pumps. The fuel dosage is due to the plunger strokes. So, the amount of mixture can vary in greater or lesser side depending on the mode of operation of the motor. Requirements for the assembly of these elements are quite high - the interface between the inner and outer surface of the cylinder should not exceed 3 μm.

The plunger pair of the injection pump has a rail in the housing. It drives the toothed sector. Due to this, the bushing (cylinder) itself is controlled. The rail is moved by the crankshaft rotation control. This achieves a dosage of cyclic feed without changing the plunger stroke.

Principle of operation

The algorithm of the action of the mechanism is based on the reciprocating movements of the two main parts. This is a piston of cylindrical shape and a bushing. During reciprocating movements, fuel is sucked into the pump. The injection takes place through special holes on the bushing. Note that the main task of the mechanism, such as a plunger, is to dose the fuel and feed it into the cylinders. In addition to the exact volume, this fuel should be supplied to the cylinders only at a certain moment. In order for the mechanism to function smoothly, high technical requirements are imposed on this pair of mechanisms. Thus, when the injection pump operates, the high pressure channels overlap between the plunger and the fuel line. This achieves a reduction in the fuel pressure, which is necessary to quickly and accurately close the nozzles of the injectors. This operation of the mechanisms prevents the appearance of fuel droplets. When the injection stroke occurs, the cone of the discharge valve rises. Further, high pressure fuel is supplied to the nebulizer, passing through the valve holder and fuel lines. When opening the drain channel, the pressure in the chamber decreases. The spring on the pressure valve presses the plunger housing against the seat. This process is cyclical. It occurs until the moment when the plunger does not restart its working stroke.

Requirements for operation

The plunger pair of the Bosch injection pump is a mechanism that requires special attention during operation. In particular, it concerns the quality of the fuel used. When running a plunger pair, it is necessary to exclude the presence of water and dust particles in the fuel. Why does this mechanism have such high requirements? Everything is very simple. When water enters the working surface of the plunger and the bushing, the lubricating film loses its integrity. As a result, the frictional force of a pair of elements increases. This leads to heating and subsequent deformation of the parts. As for particles of dust, they can cause a wedge mechanism of the plunger pair. After all, the working clearance between the cylinder and the piston is 0.0018 millimeters. It is necessary to diagnose the parts in time to prevent their premature failure. Also note that the plunger pair of the injection pump 4d56 varies in a complex manner. This is due to the high precision of manufacturing parts.

Details of faults

A frequent defect is the seizure of the plunger in the cylinder. How to diagnose the mechanism? To do this, check the plunger stroke in different positions when installing the pair at an angle of 45 degrees. The presence of corrosion marks on the work surface leads to loss of tightness. Such a malfunction is eliminated by re-fitting the mechanism. How is this done? The bush and the plunger are rubbed to a roughness of 0.1 μm. The permissible taper should not exceed 0.4 μm, and the ovality should not exceed 0.2 μm. Then the plunger pair of the injection pump is divided into size groups with an interval of 4 μm. Details are selected by the corresponding bushings. After lapping the mechanism is washed in gasoline and collected back.

The next defect is chipping or chipping at the holes. It can be accompanied by scratches, scoring and increasing the diameter of the inlet port. In this case, the wear of the working surface of the bushing is measured. Determine the conicity and ovality of the hole. If the parameter is not correct, the element must be replaced. Chipping or chipping of metal are defects that can not be repaired. How do the faults of the plunger pump of the injection pump show up? This can be determined by reducing engine power and increased fuel consumption. The unstable operation of the motor is also observed at idle.

Conclusion

So, we found out what a plunger pair is. This is an integral part of diesel fuel pumps, which operates under high pressure and doses fuel with high accuracy. The main requirements for operation are quality fuel. The operation of the plunger is adversely affected by water and dirt, which accelerates the corrosion processes and leads to the appearance of scuffing.