New High Quality Diesel Injector 7E-3384 0R-3052 7E-6408 7E-8836 7E-9983 For CAT 3500A

The pressure control mechanism of the injector works mainly in the following ways:

Mechanically controlled pressure control mechanism: mainly composed of pressure regulating spring and other components. When the engine is working, the fuel is output from the oil pump and enters the injector. When the fuel pressure is lower than the preload of the pressure regulating spring, the spring force presses the needle valve tightly against the valve seat, the spray hole is closed, and the fuel cannot be sprayed out. As the output pressure of the oil pump increases, the fuel pressure gradually increases. When the fuel pressure exceeds the preload of the pressure regulating spring, the fuel pressure overcomes the spring force, pushes the needle valve upward, opens the spray hole, and the fuel begins to spray. During the injection process, if the fuel pressure fluctuates due to changes in the output of the oil pump, the spring will stretch or compress accordingly, causing the opening of the needle valve to change, thereby adjusting the injection amount and maintaining the injection pressure relatively stable. For example, when the engine load increases and more fuel is needed, the output pressure of the oil pump rises, the fuel pressure exceeds the spring preload more, the needle valve opening increases, and the injection amount increases; conversely, when the load decreases, the output pressure of the oil pump decreases, the spring reduces the opening of the needle valve, and the injection amount decreases.

Electronically controlled pressure control mechanism: with the solenoid valve as the core component. When the engine control unit (ECU) determines that fuel injection is required based on various sensor signals, it will send an electrical signal to the solenoid valve of the injector to energize the solenoid valve. After the solenoid valve is energized, an electromagnetic force is generated to attract the armature to move and open the oil return channel. The oil chamber on the upper part of the needle valve inside the injector is connected to the oil return channel, and part of the fuel flows back to the fuel tank through the oil return channel, causing the pressure in the upper oil chamber of the needle valve to drop. The lower part of the needle valve is affected by the high-pressure fuel from the common rail pipe or the oil pump. Under the action of the upper and lower pressure differences, the needle valve overcomes the spring force and lifts up, the spray hole opens, and the fuel is sprayed out. The ECU accurately controls the oil return time and oil return amount by controlling the length of the solenoid valve power-on time, that is, the duty cycle of the pulse width modulation (PWM) signal, and then controls the pressure change of the upper oil chamber of the needle valve, and finally realizes the precise control of the injector opening time and fuel injection amount. For example, when the engine is cold started, the ECU will extend the solenoid valve power-on time, so that the needle valve is open for a longer time and more fuel is sprayed to facilitate engine starting.

In addition, in some fuel systems, a fuel pressure regulator is also equipped. There is a diaphragm inside it, which plays the role of controlling the opening and closing of the pressure valve. When the oil pressure is lower than a certain value, the pressure valve is closed, and the oil pump pressurizes the oil circuit to increase the pressure. When the pressure is higher than the specified pressure, the diaphragm opens, and the overpressure fuel flows back to the fuel tank through the return oil pipe, which plays a role in reducing pressure. Its function is to adjust the fuel pressure entering the injector according to the pressure change of the intake manifold, so that a constant pressure difference is maintained between them, so that the amount of fuel sprayed by the injector depends only on the opening time of the injector