Hot Selling Common Rail Diesel Fuel Injection Unit Pump 0 414 750 004 Engine Parts 0414750004

The working principle of the single pump is mainly based on the reciprocating motion of the plunger and the on-off control of the solenoid valve to realize the functions of fuel pressurization and injection. The following is a detailed introduction to the electronically controlled single pump as an example:

Fuel filling process: The solenoid valve is in an open state when it is not energized. At this time, the plunger moves down under the drive of the camshaft. The internal pressure of the injection system is lower than the injection pressure of the low-pressure oil circuit. The low-pressure system fuel will enter the high-pressure injection system through the oil inlet on the plunger sleeve, filling the plunger cavity with fuel.

Bypass process: When the plunger begins to rise under the action of the cam, the fuel in the plunger cavity is compressed. If the solenoid valve is still in the power-off open state, the fuel pressure in the plunger cavity is determined by the opening pressure of the return oil overflow valve, which is much lower than the opening pressure of the injector. The fuel will flow back to the fuel tank through the return oil channel. During this process, no high pressure will be established and no fuel will be injected.

Injection process: During the rise of the plunger, the electronic control unit (ECU) will send a control injection pulse signal at a specific time according to the working conditions of the engine to energize the solenoid valve. At this time, the return oil channel is closed, and the plunger cavity forms a closed volume. As the plunger continues to rise, the fuel in the closed volume is compressed, the pressure rises rapidly, and the pressure at the injector nozzle also rises sharply. When the pressure is higher than the opening pressure of the injector (about 300bar), the injector opens, and the fuel is sprayed into the combustion chamber to achieve fuel injection.

Unloading process: When the control injection pulse signal sent by the ECU ends, the solenoid valve is powered off, the return oil channel is reopened, the fuel overflows, the plunger cavity and the nozzle pressure drop rapidly, the nozzle closes, and the injection process ends, ready for the next working cycle.

In this process, the duration of the solenoid valve power supply determines the circulation fuel supply. In addition, in the static state before fuel supply, the solenoid valve coil is not powered, and the solenoid valve core is in the maximum valve opening position under the action of the reset spring, and the high and low pressure oil circuits are unblocked. When preparing for fuel supply, the solenoid valve core is quickly moved in the closing direction through high voltage and high current to prepare for the start of fuel supply. In the initial injection stage, a small gap can be left between the sealing seats of the solenoid valve core to allow a certain amount of fuel to leak into the low-pressure oil channel to achieve a lower injection pressure. The main injection area needs to completely close the solenoid valve port to quickly increase the fuel pressure in the high-pressure chamber and inject fuel at a high injection rate and high injection pressure. When the injection volume reaches the expected value, the solenoid valve coil drive current is cut off, the solenoid valve port is opened, the high and low pressure oil channels are connected, the injection pressure drops, and the injection ends.