Three-cylinder plunger pump: Operating principle of the three-cylinder plunger pump

When the three-cylinder plunger pump is operating, the cam on the fuel pump camshaft and the plunger spring act to force the plunger to move up and down, thereby accomplishing the pumping function.

Oil-Inlet Process of a Three-Cylinder Plunger Pump

As the cam’s protruding lobe rotates past, the plunger is driven by spring force to move downward. This motion creates a partial vacuum in the upper chamber of the plunger assembly—known as the primary fuel delivery chamber. When the upper end face of the plunger fully opens the inlet port in the plunger sleeve, diesel fuel stored in the fuel passages of the pump housing flows through the port and enters the delivery chamber. The plunger then continues its downward stroke until it reaches bottom dead center, at which point fuel intake is complete.

Fuel Supply Process of a Three-Cylinder Plunger Pump

When the camshaft rotates to engage the cam lobe and lift the roller, the plunger spring is compressed, causing the plunger to move upward and pressurize the fuel. A portion of the fuel then flows back through the relief port into the oil chamber of the injection pump. When the top surface of the plunger covers the upper edge of the sleeve’s inlet port, the clearance between the plunger and the sleeve is very small. (0.0015–0.0025 mm). The pump chamber at the top of the plunger becomes a sealed oil chamber. As the plunger continues to rise, the oil pressure in the pump chamber increases rapidly. When the pump pressure exceeds the residual pressure in the high-pressure fuel line caused by the spring force of the outlet valve, the outlet valve is pushed open, allowing high-pressure diesel fuel to flow through the outlet valve into the high-pressure fuel line and then into the combustion chamber via the injector.

Oil Return Process of a Three-Cylinder Plunger Pump

The plunger continuously moves upward to deliver fuel. When the plunger’s inclined groove (the cutoff edge) aligns with the return port on the sleeve, the low-pressure control oil circuit in the pumping chamber is connected to the plunger via the central and radial passages in the plunger head as well as the inclined groove, causing an abrupt drop in oil pressure. Under the action of the spring, the delivery valve quickly and promptly closes, thereby stopping fuel delivery to the system. Thereafter, as the plunger continues its reciprocating motion, once the cam’s protruding lobe has passed, the plunger returns downward under spring force, initiating the next cycle of operation.

Jiangsu Jiekai Petroleum Equipment Technology Co., Ltd. boasts sophisticated manufacturing processes, state-of-the-art production facilities, robust quality inspection capabilities, and excellent after-sales service, all of which have enabled the establishment of a comprehensive quality assurance system. Main products: Valve boxes, hydraulic ends, three-cylinder plunger pumps, oil drilling and production equipment, plunger pumps, and more—welcome to browse and select!