Difference between internal gear pump and external gear pump

Gear pump is a rotary pump which transports or pressurizes liquid by the change and movement of working volume between pump cylinder and meshing gear. Two closed spaces are composed of two gears, pump body and front and rear covers. When the gears rotate, the volume of the space on the gear disengaged side increases from small to large, forming a vacuum, sucking in the liquid, and the volume of the space on the gear meshing side changes from large to small, squeezing the liquid into the pipeline. The suction cavity and discharge cavity are separated by the meshing lines of two gears. The pressure at the discharge port of gear pump depends entirely on the resistance at the pump outlet.

 

In order to help you better understand gear pump, ZF hydraulic will introduce the difference between internal gear pump and external gear pump in detail.

 

Gear pump: gear pump is a kind of pump commonly used in hydraulic system, which is divided into external mesh pump and internal mesh pump.

 

(1) External gear pump is mainly composed of driving and driven gears, driving shaft, pump body, side plate and sealing elements. Among them, the gear meshed with each other in the pump body, the two end covers and the pump body constitute the sealing working volume. The engagement line of the gear separates the left and right cavities to form oil suction and pressure cavities. When the gear rotates in the direction shown in the figure, the gear teeth in the oil suction cavity keep disengaged from the mesh, increasing the sealing volume of the oil suction side, forming a vacuum, and sucking oil from the oil tank under the action of atmospheric pressure; when this part of oil is brought into the left oil pressure cavity by the rotating gear, the gear teeth in the cavity keep engaging, the sealing volume of the oil pressure side keeps decreasing, and the oil is pressurized, and constantly pressed out, and in Into the system, so that the completion of the gear pump oil absorption and pressure process.

 

(2) The internal gear pump is divided into involute gear shape and cycloid gear shape (rotor pump). The working principle of the internal gear pump is basically the same as that of the external gear pump, which also depends on the change of volume to achieve oil absorption and pressure. However, in order to ensure the separation of oil suction and pressure ports, a crescent separator should be added in the middle of the involute gear pump, while in the cycloid gear pump, because the two gears are only one tooth apart, the crescent separator is not needed to ensure that the oil suction and pressure are not connected when meshing.