Types of Engine Oil Pumps

The component that draws engine oil from the oil pan and pumps it under a certain pressure to the oil filter and the main oil galleries is called the oil pump. The types of engine oil pumps are:

Gear-type oil pump
Vane-type oil pump
Rotor-type oil pump

Gear-Type Oil Pump

Inside the pump are two intermeshed gears. One gear is the driving gear, the other is the driven gear. The driving gear takes its motion from the camshaft in some engines and from the crankshaft in others. As the gears rotate, oil coming from the inlet passage fills the gaps between the teeth and is carried to the outlet passage. The amount of oil carried depends on the rotational speed of the gears and the thickness of the oil.

How does a gear-type engine oil pump work?

Disassembled view and operation of a gear-type oil pump

When the engine oil is cold, or as engine speed increases, the amount of oil carried by the gears becomes more than necessary. To prevent oil pressure from rising above a certain value, a pressure relief valve is placed in the outlet passage. The pressure relief valve can be located in the pump body or on the main oil gallery. When the pump’s outlet oil pressure rises enough to overcome the spring pressure of the relief valve, the valve opens and allows the oil to return.

Vane-Type Oil Pump

In a vane-type oil pump, vanes are used instead of gears. The vanes are fitted into slots in a rotor that spins off-center within the pump housing. Springs inside the slots keep the vanes continuously in contact with the housing surface.

The vane rotor is connected to the pump shaft. As the shaft rotates, the vanes create a volume that grows in front of the inlet passage and shrinks to zero in front of the outlet passage. As the volume carrying the oil drops to zero, the oil is forced into the main oil gallery.

Rotor-Type Oil Pump

In a rotor-type oil pump, an inner rotor sits in the rotor housing, and as the pump shaft turns, the outer rotor, which works together with the inner rotor, creates a variable volume that grows at the oil inlet passage and shrinks to zero at the oil outlet passage.

Oil drawn into the large volume at the inlet passage is forced into the main oil galleries as the volume drops to zero at the outlet passage.

In this article, we took a look at the types of engine oil pumps and how they work. Supported by animations, we examined the types of engine oil pumps and their operating systems. See you in our next articles.

Gear-Type Oil Pump

Gear-type oil pumps are the most commonly used type in automotive engines thanks to their simple design and reliability.

Rotor-Type Oil Pumps

Rotor (gerotor) type pumps are frequently preferred in modern engines thanks to their compact design.

Pressure Relief Valve

The pressure relief valve in oil pumps protects the system by draining excess oil when overpressure occurs.

Related Questions

Oil that enters the gaps between the rotating gears is physically carried from the inlet passage to the outlet passage as the gears turn. This simple but effective mechanism ensures the oil is pumped in a continuous, steady flow.

As engine speed increases, the amount of oil the pump carries also increases, which can lead to excessive pressure in the system. The pressure relief valve opens above a certain pressure to return the excess oil and keep the pressure at a safe level.