Basic introduction
The electronically controlled injector is the most critical and complex component of the common rail system and the most difficult part of the design and process. By controlling the opening and closing of the solenoid valve, the ECU injects the fuel in the high-pressure fuel rail into the combustion chamber with the optimum injection timing, fuel injection amount and fuel injection rate. In order to achieve an effective fuel injection starting point and precise fuel injection, the common rail system uses a dedicated injector with a hydraulic servo system and electronic control components (solenoid valves).
The injector consists of a hole injector similar to a conventional injector, a hydraulic servo system (control piston, control orifice, etc.), solenoid valve, and so on.

Working principle
The diesel fuel injection system atomizes the fuel and distributes the components that are mixed with the air in the combustion chamber. It consists mainly of the injector and the injector body. The mounting position and angle on the cylinder head depends on the design of the combustion chamber.
Injectors are available in both open and closed versions. The open injector has a simple structure but poor atomization and is rarely used. Closed injectors are widely used in a variety of diesel engines. The diesel engine draws in pure air during the intake stroke. When the compression stroke is nearing the end, the diesel fuel is raised to 100 MPa or more by the fuel injection pump, and is injected into the cylinder through the injector to mix with the compressed high-temperature air in a short time to form a combustible mixture. Since the compression ratio of the diesel engine is high (generally 16-22), the air pressure in the cylinder can reach 3.5-4.5MPa at the end of compression, and the temperature is as high as 750-1000K (while the gas pressure of the gasoline engine at this time will be 0.6-1.2MPa, the temperature reaches 600-700K), which greatly exceeds the auto-ignition temperature of diesel. Therefore, after being injected into the cylinder, the diesel fuel is automatically ignited and burned after being mixed with the air in a short time. The air pressure in the cylinder rises rapidly to 6-9 MPa and the temperature rises to 2000-2500K. Under the push of high pressure gas, the piston moves downward and drives the crankshaft to rotate, and the exhaust gas is also discharged into the atmosphere through the exhaust pipe.

Classification introduction
(1) Shaft needle type electromagnetic injector.
When the fuel is injected, the armature drives the needle valve to rise from its seat surface by about 0.1 mm, and the fuel is ejected from the precision gap. In order to fully atomize the fuel, a needle of the injection shaft is ground at the front end of the needle valve. The injector suction and fall time is about 1 to 1.5 ms.
(2) Ball valve type electromagnetic injector
The valve needle of the ball valve is light in weight and has a large spring preload force for a wider dynamic flow range. The ball valve has an automatic centering function and good sealing. At the same time, the ball valve simplifies the structure of the metering part and helps improve the accuracy of the fuel injection.
(3) Chip valve type electromagnetic injector.
The light-weight valve and bore seats are combined with a magnetically optimized injector assembly that allows the injector to have a wide dynamic flow range and high resistance to clogging.
(4) Injector with lower oil inlet.
By adopting the bottom oil supply mode, since the fuel can continuously flow out from the upper portion of the injector through the inner cavity of the injector, the cooling effect on the metering portion of the injector is very obvious, so that the generation of the air resistance can be effectively prevented, and the hot start reliability of the automobile can be improved. In addition, the fuel injector with bottom injection eliminates the need for a fuel manifold and helps reduce costs.

Maintenance method

1. We must properly maintain the accessories of the fuel injection pump.

2. It is necessary to check frequently whether the amount of oil in the fuel pump oil pool and its quality meet the requirements.

3. It is necessary to regularly check and adjust the oil supply of each cylinder of the fuel injection pump.

4. Use standard high pressure oil pipes.

5. It is necessary to check the sealing condition of the valve parts on a regular basis.

6. Replace the worn plunger and the oil delivery valve couple in time.

7. The diesel oil should be used and filtered to ensure that the diesel fuel entering the fuel injection pump is highly clean.

8. Regularly check and adjust the fuel supply advance angle and the oil supply interval angle of each cylinder.

9. Check the camshaft clearance regularly.

10. Regularly check the wear of the relevant keyway and fixing bolts.