English
Structural Composition
Pump oil mechanism: It mainly consists of piston components and oil outlet valve components, etc. The piston component is composed of the piston and the piston sleeve, which is a key part of the fuel injection pump. The two components are precisely matched to achieve the pressurization and metering of fuel. The oil outlet valve component controls the unidirectional flow of fuel, ensuring that the fuel enters the high-pressure fuel pipe at the appropriate time.
Fuel supply quantity regulating mechanism: Common types include the rack-type fuel quantity regulating mechanism and the rocker-type fuel quantity regulating mechanism. The fuel supply quantity is adjusted by changing the effective stroke of the plunger to meet the requirements of diesel engines under different operating conditions.
Drive mechanism: Composed of camshaft, pushrod assembly, etc. The camshaft is driven by the crankshaft gear of the engine. The raised part of the cam drives the plunger to move up and down, providing power for oil pumping.
Injection pump body: It serves as the installation base for the oil pump mechanism, the fuel supply quantity regulating mechanism, and the driving mechanism. It must possess sufficient strength, rigidity, and sealing properties, and be convenient for disassembly, adjustment, and maintenance.
Working principle
Oil suction process: The plunger is driven by the cam on the camshaft. When the raised part of the cam leaves the plunger, the plunger moves downward under the action of the plunger spring, and the volume of the oil chamber increases while the pressure decreases. When the radial oil inlet holes on the plunger sleeve are exposed, the fuel in the low-pressure oil chamber flows through the inlet holes into the pump chamber.
Oil pumping process: When the raised part of the cam pushes the plunger up, the volume in the pump chamber decreases and the pressure increases. The fuel flows back into the low-pressure oil chamber through the radial oil holes on the plunger sleeve. When the plunger moves upward and completely blocks the radial oil holes on the plunger sleeve, the pressure in the pump chamber increases rapidly. When this pressure overcomes the preload of the oil outlet valve spring, the oil outlet valve moves upward. When the pressure relief ring band on the oil outlet valve leaves the valve seat, the high-pressure diesel is pumped into the high-pressure oil pipe and then sprayed into the cylinder through the fuel injector.
Return oil process: As the plunger continues to move upward, when the inclined groove on the plunger communicates with the radial oil hole on the plunger sleeve, the fuel in the pump chamber flows back through the axial oil passage, inclined oil passage and oil hole on the plunger sleeve to the low-pressure oil chamber, and the oil pumping stops.
Classification
Plunger-type fuel injection pump: The oldest and most widely used type, it has high reliability. The process of oil suction, pressure application and return is achieved through the reciprocating motion of the plunger within the plunger sleeve. It precisely controls the fuel injection volume and timing.
Fuel Injection Pump - Injector: Integrating the fuel injection pump and the injector into one unit, it is directly installed on the cylinder head and driven by the overhead camshaft. The high-pressure fuel pipe connecting the injector and the pump is omitted, effectively eliminating the adverse effects brought by the high-pressure fuel pipe, thereby making the fuel injection more precise and efficient.
Rotary distributor type fuel injection pump: It has only one pair of plungers. It mainly relies on the rotation of the rotor to achieve fuel pressurization and distribution. It has the characteristics of small size, light weight, convenient use and low cost, and is suitable for small cars and some engines with high requirements for space layout.
Function
Increase oil pressure: Raise the injection pressure to 10MPa - 20MPa, so that the fuel can be injected into the cylinder with sufficient pressure, achieving good atomization and combustion.
Control the injection timing: According to the working sequence of the diesel engine, inject fuel and stop the injection at the specified time to ensure that the combustion of the fuel in the cylinder occurs at the correct moment.
Control fuel injection volume: Based on the operating conditions of the diesel engine, such as load and speed, adjust the amount of fuel injection to regulate the engine's speed and power, so as to meet different working requirements.
Debugging and Maintenance
Debugging method: This includes the debugging of fuel supply time, starting oil quantity, rated speed fuel supply quantity, and idle fuel supply quantity, etc. By adjusting relevant components and parameters, the working performance of the fuel injection pump can be optimized to the best state.
Maintenance points: When installing the fuel injection pump, check and adjust the fuel supply advance angle; use standard light diesel oil and filter it through sedimentation; keep the diesel tank and diesel filter clean; regularly inspect the engine oil in the governor and replenish or replace it in time; prevent oil leakage from the fuel injection pump and fuel pump, etc.
