The core working principle of a gear pump is "volumetric suction and discharge" - by rotating a pair of meshing gears, a periodic sealed chamber volume change is formed inside the pump body. Through the process of "vacuum suction and extrusion discharge", mechanical energy is converted into pressure energy and kinetic energy of the fluid, achieving directional fluid transportation.

The working process can be divided into three continuous and cyclic steps: suction, transportation, and discharge. Combining structural details can provide a clearer understanding:

1、 First, clarify the core structure (the basis of the principle)

The coordination of key components of gear pumps is a prerequisite for realizing the principle:

A pair of mutually meshing gears (driving gear+driven gear, usually external meshing, with a few internal meshing);

Closed pump body+front and rear end caps: The gap between the gear teeth and the inner wall of the pump body, and between the gear end face and the end cap, is extremely small (usually 0.02~0.05mm), forming a "sealed chamber";

Two interfaces: suction port (low-pressure area, connected to the oil tank/fluid source) and discharge port (high-pressure area, connected to the output pipeline). The suction and discharge ports are separated by meshing gears and are not connected to each other.

2、 Detailed working process (three-step cycle)

1. Liquid suction stage: Vacuum negative pressure "sucked in"

The motor drives the driving gear to rotate, and the driving gear drives the driven gear to rotate synchronously in the opposite direction through tooth meshing;

When the gear rotates to the suction port side, the meshing teeth gradually "separate" - the originally meshing tooth surfaces come out of contact, and the "inter tooth groove" (groove between gear teeth) of the gear is exposed, suddenly increasing the volume of the sealing chamber formed with the pump body and end cover;

The increase in sealed chamber volume leads to a decrease in internal pressure, forming a negative vacuum pressure;

External fluids (such as oil and slurry) are "sucked" into the suction port under atmospheric pressure or inlet pressure, filling the space between the teeth grooves.

2. Transportation stage: sealed and carried "sent over"

The gear continues to rotate, and the interdental grooves filled with fluid are carried from the suction port side to the discharge port side as the gear rotates;

During this process, the fluid in the interdental groove is sealed between the groove and the pump body - because the clearance between the gear tooth tip and the inner wall of the pump body, as well as between the tooth end face and the end cover, is extremely small, the fluid cannot leak back to the oil suction port, nor will it flow into the oil discharge port in advance, achieving "no backflow delivery".

3. Drainage stage: Squeezing and pressurizing to "press out"

When the interdental groove carrying fluid rotates to the side of the oil discharge port, the separated gear tooth surface begins to "mesh" again;

The meshing teeth will gradually squeeze the fluid in the inter tooth groove - the volume of the sealing chamber is continuously "compressed" by the meshing part of the gear, and the volume rapidly decreases;

The fluid cannot be compressed, and the decrease in volume leads to a sharp increase in internal pressure;

When the pressure exceeds the pipeline resistance of the oil outlet, high-pressure fluid is "forced out" of the oil outlet and transported to subsequent systems (such as hydraulic actuators, lubrication pipelines, etc.).

The gear continues to rotate, and the above three steps will cycle back and forth to achieve continuous and stable fluid transport.

3、 The key support of the principle (why can it work stably?)

Sealing is the core: the small gaps between the tooth tip and the inner wall of the pump body, as well as between the tooth end face and the end cover, ensure the "sealing" of the sealing chamber. If the gaps are too large, the fluid in the high-pressure area will leak back into the low-pressure area (known as "internal leakage"), resulting in a decrease in pressure and insufficient flow rate;

Mesh plays a separating role: The gear teeth that are always in mesh act like a "dynamic sealing wall", strictly separating the oil suction port (low-pressure area) and the oil discharge port (high-pressure area) to avoid direct communication of high and low-pressure fluids;

The source of quantitative characteristics: For each rotation of the gear, the total volume of the interdental groove is fixed - therefore, the output fluid volume (displacement) is fixed. As long as the speed is stable, the flow rate is highly uniform (this is also the principle of "quantitative delivery" of gear pumps);

The essence of self-priming ability: The vacuum negative pressure during the suction stage allows the gear pump to start suction without the need to pre pump (exhaust all air), which is the core of its self-priming ability (provided that it is well sealed and there is no significant air leakage).

4、 Addendum: Principle differences of internal gear pumps (brief)

In addition to the common external gear pump, there is also an internal gear pump (a large gear wrapped around a small gear, with the same direction of rotation), and the principle is essentially the same:

Liquid suction: The tooth surfaces of the small and large gears separate, and the sealing chamber volume increases, allowing for liquid suction;

Transport: The fluid is carried by the interdental groove to the discharge side;

Drainage: tooth surface meshing extrusion volume, drainage;

Differences: The clearance between internal meshing is smaller, the noise is lower, and the flow pulsation is smaller, making it suitable for high-pressure and low-noise scenarios.