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common rail work

common rail work

The adjustment of injection time and injection quantity is realized by electronically triggered injector. These injectors replace the injector cap assembly (injector and injector cap).
Similar to the nozzle cap assembly in the existing direct injection diesel engine, the pressure tool is also applied to the top of the cylinder for installing the fuel injector, that is, the fuel injector of the common rail can be installed on the top of the cylinder of the existing direct injection diesel engine without changing the engine. The fuel injector can be divided into a series of functional components: orifice nozzle, hydraulic servo system and solenoid valve.
The fuel comes from the high-pressure oil circuit, flows to the fuel injection nozzle through the channel, and flows to the control chamber through the orifice. The control chamber is connected with the fuel circuit through a drain hole controlled by the solenoid valve. When the oil drain hole is closed, the hydraulic pressure acting on the needle valve control piston exceeds its force on the pressure bearing surface of the needle valve of the fuel injection nozzle. As a result, the needle valve is forced to enter the valve seat and isolate the high-pressure channel from the combustion chamber for sealing.
When the solenoid valve of the fuel injector is triggered, the oil drain hole is opened, which causes the pressure of the control chamber to drop. As a result, the hydraulic pressure on the piston also drops. Once the hydraulic pressure drops below the force acting on the pressure bearing surface of the needle valve of the fuel injector, the needle valve is opened and the fuel is injected into the combustion chamber through the nozzle hole. This indirect control of the injector needle valve adopts a set of hydraulic pressure amplification system, because the force required to quickly open the needle valve cannot be directly generated by the solenoid valve. The so-called control function required to open the needle valve is to open the oil drain hole through the solenoid valve to reduce the pressure in the control chamber, so as to open the needle valve.
In addition, the fuel also leaks at the needle valve and control plunger. The leaked fuel flows back to the fuel tank together with the return oil of high-pressure pump and pressure control valve through the return pipe. When the engine is running and the pressure generated by the high-pressure pump, divide the working process of the fuel injector
It is divided into four stages:
-The fuel injector is closed (when there is high pressure);
-Fuel injector on (start injection);
-The fuel injector is fully opened;
-Injector off (end of injection).
These working stages are caused by the distribution of force acting on various parts of the fuel injector. When the engine is stopped and there is no pressure in the common rail, the fuel injector spring closes the fuel injector. Fuel injector off (free state): in the free state, the solenoid valve is not energized, so it is off.
The oil drain hole is closed, the spring of the valve makes the pivot ball top on the oil drain hole seat, the common rail high pressure is established in the valve control chamber, and the same pressure also exists in the pressure chamber of the fuel injection nozzle. The common rail pressure acts on the end face of the control piston and acts together with the spring force of the fuel injection nozzle to overcome the pressure generated by the pressure chamber
The opening force maintains the fuel injection nozzle in the closed position.
Fuel injector on (start injection): the fuel injector is in its free state, and the solenoid valve is connected to ensure the peak current of its rapid opening.
The force generated by the electromagnetic trigger exceeds the spring force of the valve, and the trigger opens the oil drain hole. Almost at the same time, the higher pickup current decreases to the maintenance current required by the lower electromagnet, and the magnetic gap of the magnetic circuit becomes smaller, so that only a small maintenance current is required to keep the control valve open. When the drain hole is opened, the fuel will flow from the valve control chamber into the cavity above it, and the fuel will return to the tank through the return pipe. The oil drain hole destroys the absolute pressure balance, and finally the pressure in the valve control chamber also decreases. This causes the pressure in the valve control chamber to be lower than that in the pressure bearing chamber of the fuel injection nozzle which still has the same pressure level as the common rail. The reduction of the pressure in the valve control chamber leads to the reduction of the force acting on the control piston. Finally, the needle valve of the fuel injection nozzle opens and the injection begins.
The opening speed of the needle valve of the fuel injection nozzle depends on the different flow through the oil inlet and drain holes of the control chamber. The control piston reaches the upper stop position, which is still held by the buffer generated by the fuel flow between the inlet and outlet ports. At this time, the fuel injector nozzle is fully opened and the fuel is injected into the combustion chamber at almost the same pressure as that in the common rail. The forced distribution of the fuel injector is similar to that during the opening phase.
Injector off (end of injection): once the solenoid valve is not triggered and the valve spring moves the pivot downward, the ball valve will close the oil drain hole. The pivot is designed into two elements. Although the pivot disc is guided by a driving shoulder during its downward movement, it can buffer the return spring with the offset spring, so as to minimize the downward force on the pivot and ball valve. When the oil drain hole is closed, the oil drain port, and the fuel enters the control chamber through the oil inlet to establish pressure. This pressure is the same as the pressure in the common rail. This pressure generates an increased force on the end face of the control piston. This force plus the spring force exceeds the force generated by the pressure chamber, so the needle valve of the injector is closed. The closing speed of the injector needle valve depends on the flow of the oil inlet hole. Once the injector needle valve moves to the bottom sealing position, the injection stops.

ed, which causes the pressure of the control chamber to drop. As a result, the hydraulic pressure on the piston also drops. Once the hydraulic pressure drops below the force acting on the pressure bearing surface of the needle valve of the fuel injector, the needle valve is opened and the fuel is injected into the combustion chamber through the nozzle hole. This indirect control of the injector needle valve adopts a set of hydraulic pressure amplification system, because the force required to quickly open the needle valve cannot be directly generated by the solenoid valve. The so-called control function required to open the needle valve is to open the oil drain hole through the solenoid valve to reduce the pressure in the control chamber, so as to open the needle valve.
Figure 8 common rail system injector
1 – oil return pipe; 2 – return spring; 3 – coil; 4 – high voltage connection;
5 – pivot disc; 6 – ball valve; 7 – oil drain hole; 8 – control chamber; 9 – oil inlet
Mouth; 10 – control piston; 11 – oil nozzle shaft needle; 12 fuel injection nozzle
Figure 1 – fuel injector off Figure 2 – fuel injector on
In addition, the fuel also causes leakage at the needle valve and control plunger. Control and leak the fuel through
Through the oil return pipe, it flows back to the oil tank together with the return oil of the high-pressure pump and pressure control valve.
When the engine is running and the pressure generated by the high-pressure pump, divide the working process of the fuel injector
It is divided into four stages:
-The fuel injector is closed (when there is high pressure);
-Fuel injector on (start injection);
-The fuel injector is fully opened;
-Injector off (end of injection).
These working stages are caused by the distribution of force acting on various parts of the fuel injector. launch
When the engine is shut down and there is no pressure in the common rail, the fuel injector spring closes the fuel injector. Fuel injector off (free state): in the free state, the solenoid valve is not energized, so it is
It’s closed.
The oil drain hole is closed, the spring of the valve makes the pivot ball top on the oil drain hole seat, the common rail high pressure is established in the valve control chamber, and the same pressure also exists in the pressure chamber of the fuel injection nozzle. The common rail pressure acts on the end face of the control piston and acts together with the spring force of the fuel injection nozzle to overcome the pressure generated by the pressure chamber
The opening force maintains the fuel injection nozzle in the closed position.
Fuel injector on (start injection): the fuel injector is in its free state, and the solenoid valve is used for injection
Peak current to ensure its fast opening.
The force generated by the electromagnetic trigger exceeds the spring force of the valve, and the trigger opens the oil drain hole. Almost at the same time, the higher pickup current decreases to the maintenance current required by the lower electromagnet, and the magnetic gap of the magnetic circuit becomes smaller, so that only a small maintenance current is required to keep the control valve open. When the drain hole is opened, the fuel will flow from the valve control chamber into the cavity above it, and the fuel will return to the tank through the return pipe. The oil drain hole destroys the absolute pressure balance, and finally the pressure in the valve control chamber also decreases. This causes the pressure in the valve control chamber to be lower than that in the pressure bearing chamber of the fuel injection nozzle which still has the same pressure level as the common rail. The reduction of the pressure in the valve control chamber leads to the reduction of the force acting on the control piston
Finally, the needle valve of the fuel injection nozzle opens and the injection starts.
The opening speed of the needle valve of the fuel injection nozzle depends on the different flow through the oil inlet and drain holes of the control chamber. The control piston reaches the upper stop position, which is still held by the buffer generated by the fuel flow between the inlet and outlet ports. At this time, the fuel injector nozzle is fully opened and the fuel is injected into the combustion chamber at almost the same pressure as that in the common rail. The forced distribution of the injector is related to its opening step
The time is similar.
Injector off (end of injection): once the solenoid valve is not triggered and the valve spring moves the pivot downward, the ball valve will close the oil drain hole. The pivot is designed as two elements, although the pivot disc is in its direction
The downward movement is guided by a driving shoulder, but it can use the offset spring to buffer the return spring, so as to minimize the downward force on the pivot and ball valve. When the oil drain hole is closed, the oil drain port, and the fuel enters the control chamber through the oil inlet to establish pressure. This pressure is the same as the pressure in the common rail. This pressure generates an increased force on the end face of the control piston. This force plus the spring force exceeds the force generated by the pressure chamber, so the needle valve of the injector is closed. The closing speed of the injector needle valve depends on the flow of the oil inlet hole. Once the injector needle valve moves to the bottom sealing position
When set, the injection stops.

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