Hydraulic fluid is pumped by mechanisms that create a pressure difference, typically involving a changing volume within a chamber to draw fluid in and then push it out.
Understanding Hydraulic Fluid Pumping
At its core, pumping hydraulic fluid involves moving a liquid from one place to another, usually under pressure, to power hydraulic systems. This process relies on positive displacement principles in most hydraulic pumps. These pumps trap a specific volume of fluid and force it into the system, regardless of the pressure on the outlet side (up to the pump's design limits).
Different types of pumps achieve this through various mechanical actions. The provided reference describes the operation of a vane pump, illustrating a common method.
The Vane Pump Mechanism
A vane pump works by using a rotor with sliding vanes placed inside a larger housing. The rotor is offset from the center of the housing. As the rotor spins, the vanes extend and retract, creating chambers of varying size between the vanes, the rotor, and the housing.
Here's how the pumping action occurs, incorporating the information from the reference:
1. Fluid Intake (Inlet Side)
- As the rotor turns, the space or chamber enclosed by the vanes, rotor, and housing begins to increase in volume.
- This expansion creates a vacuum within the chamber.
- Due to this vacuum and the atmospheric pressure (or system pressure) acting on the reservoir fluid, oil is forced into this expanding space. This occurs on the inlet side of the pump.
2. Fluid Discharge (Outlet Side)
- As the rotor continues to turn, the vanes sweep towards the side where the rotor and housing are closer together.
- In this part of the rotation, the space or volume enclosed by the vanes, rotor, and housing reduces.
- As the volume shrinks, the trapped liquid is forced out through the discharge ports, sending pressurized fluid into the hydraulic circuit.
This continuous cycle of volume increase (intake) and volume decrease (discharge) allows the vane pump to efficiently move hydraulic fluid and build pressure.
Pump Cycle Stages
We can summarize the process in a simple table:
| Stage | Chamber Volume | Pressure Effect | Fluid Movement | Side of Pump |
|---|---|---|---|---|
| Intake | Increases | Creates Vacuum | Fluid Enters | Inlet |
| Discharge | Reduces | Builds Pressure | Fluid Exits | Outlet |
Other Pump Types (Brief Mention)
While the vane pump is one example, hydraulic fluid can also be pumped by other mechanisms, such as:
- Gear Pumps: Use meshing gears to trap and move fluid.
- Piston Pumps: Use reciprocating pistons inside cylinders to draw in and push out fluid, often capable of very high pressures.
Each type uses a different mechanical method to achieve the fundamental action of trapping and displacing fluid volumes.
Key Takeaway
Regardless of the specific design, hydraulic pumps operate by creating enclosed volumes that expand to draw fluid in and then contract to force the fluid out under pressure, providing the power needed for hydraulic systems. The vane pump described in the reference exemplifies this principle by using rotating vanes to create changing chamber volumes.
