High Quality Check Valve Assembly for C7 C9 Control Valve Injector Diesel Engien Auto Parts

Working Principle
When the fuel flows from the oil pump to the injector, the oil pressure acts on the valve core of the one-way valve. When the oil pressure reaches a certain value, which is enough to overcome the elastic force of the spring, the valve core is pushed open, and the fuel enters the injector through the one-way valve, ready for injection. When the oil pump stops supplying oil or the oil pressure drops, the spring force resets the valve core, closes the one-way valve, and prevents the fuel from flowing back, thereby maintaining the pressure in the fuel system stable and preventing the fuel from flowing back to the oil pump or tank.

Function
Preventing fuel backflow: This is the most important function of the one-way valve. It ensures that the fuel can only flow in the direction from the oil pump to the injector, avoiding the fuel from flowing back to the oil pump or other components when the engine stops running or the pressure in the fuel system changes, ensuring the stability of the pressure in the fuel system, and helping the engine to quickly establish normal fuel pressure when it starts next time, so as to achieve a quick start.
Protecting the oil pump: The one-way valve installed at the outlet of the injection pump can prevent the sudden increase in system pressure from damaging the oil pump. When the needle valve of the injector is closed, the pressure in the fuel system will rise sharply. If there is no one-way valve, this pressure shock may be transmitted to the oil pump, causing damage to the seals, plungers and other components of the oil pump. The one-way valve can effectively alleviate this pressure shock and extend the service life of the oil pump.
Cooperate to achieve specific functions: When used in conjunction with a throttle valve, a pressure reducing valve or a pressure valve, some specific functions can be achieved. For example, in parallel with a throttle valve or a pressure reducing valve, the forward slow speed and reverse fast speed functions of the actuator can be constructed, or a forward deceleration and reverse free flow circuit can be realized; when connected in series with a pressure valve, the pressure can be gradually increased to prevent the adverse effects of pressure reaction on the system.

Common types
Isovolumetric oil outlet valve: simple structure, there is a circle of pressure relief belt under the sealing seat surface, and the seat surface sealing belt and the pressure relief belt together form a pressure relief volume. When the oil supply is completed, the pressure in the high-pressure system can be rapidly reduced to prevent secondary injection, but it lacks the ability to respond, and excessive or insufficient pressure relief may occur under different working conditions.
Isobaric oil outlet valve: A set of one-way valves consisting of isobaric valves and springs is installed in the oil outlet valve core. It can automatically adjust the residual pressure after the oil supply is completed under various working conditions to keep it at a certain level higher than the atmospheric pressure. It has good performance, but the structure is relatively complex.
Damping oil outlet valve: A damping valve is usually installed on the isochoric oil outlet valve, and a throttling hole is opened on it. It can slow down the seating speed of the oil outlet valve, delay the pressure drop speed, prevent the generation of bubbles and reduce cavitation, and at the same time attenuate the reflected wave to prevent secondary injection. The structure is simple, but the residual pressure in the high-pressure oil pipe still changes with the working conditions.
Buffering oil outlet valve: The traditional oil outlet valve is designed into two parts, the upper part is used for unloading, and the lower part has an oil outlet valve cone and a flange for buffering. The fuel discharge is controlled by the gap between the upper and lower flanges, the seating speed of the oil outlet valve is slowed down, and the pressure fluctuation in the later stage of injection is alleviated, but the dynamic response is worse than that of the isobaric oil outlet valve.
Orifice-type oil outlet valve: The high-pressure oil pipe can be directly connected to the oil outlet valve housing, significantly reducing the volume of the high-pressure chamber. When the oil supply stops and the oil outlet valve is seated, the high-pressure oil pipe is connected to the plunger chamber through the throttle hole, and the fuel flow is controlled through the throttle hole to prevent bubbles from being generated after the oil outlet valve is seated and the reflected wave is attenuated. It has good working reliability and long service life.
Throttling oil outlet valve: The valve body, oil outlet valve spring and spring seat are replaced by a reducer. The throttling effect is used to reduce the amplitude of the pressure wave reflected from the fuel injection nozzle, prevent the needle valve from opening again, and increase the injection pressure without increasing the load on the cam transmission mechanism of the fuel injection pump.