Characteristics of Plunger Type Fuel Injection Pump for Diesel Engine 2

This article continues to introduce to users how plunger fuel injection pumps meet the working requirements of diesel engines.

For multi cylinder fuel injection pumps, if the fuel supply of each cylinder is inconsistent, adjustments must be made. The methods of adjustment vary depending on the structure. If a fork type fuel control mechanism is used, the fuel supply can be adjusted by changing the position of the adjustment fork on the rod.

(3) To ensure good atomization quality, the fuel injection pressure of diesel engines can reach up to 12-100MPa. To establish such a high fuel pressure, the upper oil chamber of the plunger and the part connected to the injector must have good sealing, which requires high fitting accuracy between the plunger and the plunger sleeve. Usually, the gap between them is only 0.0015~0.0025mm. Therefore, plunger fittings (pairs) are selected in pairs and ground, and any part of the fittings cannot be interchanged with other parts.

The sealing performance of the plunger coupling of the fuel injection pump is a basic condition for ensuring high fuel supply pressure, while the actual fuel injection pressure is limited by the pressure regulating spring of the fuel injector. Adjusting the preload force of the pressure regulating spring can change the level of fuel injection pressure.

(4) Oil supply simply starts and ends quickly and decisively. On the upper end face of the plunger coupling, there is another pair of precision coupling parts (oil outlet valve and oil outlet valve seat), called the oil outlet valve pair. The main function of the fuel outlet valve is to enable the fuel injection pump to start supplying fuel in a timely and rapid manner, and to stop the fuel quickly and cleanly.

The upper part of the oil outlet valve has a conical surface, and the oil outlet valve spring presses this conical surface against the oil outlet valve seat, isolating the upper space of the plunger from the high-pressure oil pipe. There is a cylindrical ring at the lower part of the conical surface called the decompression ring, which is connected to the outlet

The inner hole of the oil valve seat is precisely matched and also has a sealing effect. The valve stem under the pressure relief ring has four straight grooves milled on top, making the cross-section cross shaped. The cross section serves as a guide during the lifting and lowering of the oil outlet valve, while the four grooves are the pathways for diesel fuel. When the plunger starts to press the oil until the diesel pressure exceeds the elastic force of the outlet valve spring, the outlet valve starts to rise but does not release oil. When the outlet valve rises to the lower edge of the pressure reducing ring and leaves the outlet valve seat hole, high-pressure diesel flows through the cross groove and high-pressure oil pipe to the injector, causing fuel supply to quickly begin.

When the edge of the plunger groove is connected to the oil return hole, high-pressure diesel flows back into the low-pressure oil chamber. The oil outlet valve rapidly drops under the joint action of the oil outlet valve spring and high-pressure diesel, and the oil pressure in the high-pressure oil pipe rapidly decreases.

When the lower edge of the pressure relief ring enters the inner hole of the oil outlet valve seat, the oil chamber on the upper part of the plunger is separated from the high-pressure oil pipe. As the delivery valve continues to descend until the conical surface is seated, a portion of the volume of the high-pressure oil chamber above the delivery valve is released. As a result, the volume of the oil chamber in the high-pressure oil pipe suddenly increases, the oil pressure rapidly decreases, and the fuel injection immediately stops. This ensures the atomization quality of the fuel in the later stage of injection and prevents secondary injection and dripping. In addition, due to the tight fit between the conical surface of the oil outlet valve and the valve seat, a certain amount of diesel can be retained in the high-pressure oil pipe and a certain residual pressure can be maintained, making the next fuel supply faster and the fuel supply more uniform and stable. If the pressure relief ring is worn or the clearance is too large, resulting in poor sealing, it will lead to deterioration of the working performance of the diesel engine. The oil outlet valve pairs are also paired and finely ground components, and cannot be replaced arbitrarily during use.

Dingbo Power was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to sales@dieselgeneratortech.com we will pay highly attention on your question.