How do oil pumps work?

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Originally Posted By: bulwnkl
Interesting. What sort of pumps are they, in cars? Piston pumps? What are some example cars which use a variable-displacement oil pump?


regular pumps are usually positive displacement gerotor
type

the pentastar has(taken from pentastar.com)

Quote:

The advanced oil filter system eliminates oil spills, thanks to an incinerable filter element instead of the typical spin-on filters; the filter is conveniently located on top of the engine.

A chain-driven, vane-type variable displacement oil pump adjusts the flow rate and pressure as commanded by the engine management system, which uses a solenoid to drive the pump into low or high pressure mode. For example, below 3,500 rpm, the pump conserves energy by using low pressure; at speeds over 3,500 rpm, the pump switches to high pressure.

A force balance mechanism inside the oil pump adjusts the size of the pumping chambers to alter oil flow. If the oil is cold, the pump reduces the size of the internal chambers. When the oil is hot and thinner, more oil is needed, and a spring increases the size of the pump chambers. This also saves energy.

The pump is driven at a 1:1 drive ratio; its location under the block is more efficient than an on-crankshaft location. An internal, mechanical ball-and-spring relief valve dumps oil into the sump when needed, for conditions such as a cold start with high engine speed. Both pump and pressure regulation solenoid are non-serviceable.
 
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