Automotive Lubrication: A Look at Three Oil Pump Designs
Within an automotive engine, a pump circulates lubricating oil through lines or passages to reach moving components, which reduces friction-related wear between metal surfaces and helps carry away heat. Which oil pump design an engine uses is determined by its construction, how the pump is driven, and what its lubrication needs are. The lubrication setup also differs based on how the vehicle is used, whether that is an ordinary passenger car or an off-road vehicle.
By Morgan Foster
A pump serves as an essential component of an automotive system by moving lubricating oil through pipes or ducts to the engine's various moving parts. This circulation serves to reduce wear caused by metal-to-metal friction and to help displace heat. The choice of oil pump for a given automotive engine is influenced by the engine's structure, the drive method, and its lubrication demands. Lubrication systems also differ depending on the vehicle's intended application, such as a standard passenger car versus an off-road vehicle.
Gear Pump
The gear pump functions on the same concept as a water wheel. It relies on two wheels to generate high pressure within the oil pan and push oil to every location requiring lubrication. Because engines run at high speeds, sufficient pressure is needed for oil to reach all moving components. Within the pump, two interlocking wheels pull oil from the pan and drive it into a comparatively smaller space, thereby building the necessary pressure. The design of the wheels or gears and the pump walls ensures that once high pressure builds near the delivery nozzle, oil cannot return to the oil pan.
Rotary Pump
A rotary pump shares its underlying principle with the gear pump. It regulates oil flow into the engine using two rotating sprockets. However, the mechanism that pressurizes the oil and injects it into the system differs somewhat. Rather than building pressure by adding more oil at the nozzle end, the rotors pull a quantity of oil into a compartment that steadily shrinks, compressing the oil and generating pressure close to the injection nozzle. This effect is produced by varying the teeth sizes on the rotor, which alters the compartment dimensions as it turns.
Crescent Pump
The crescent pump offers an advantage when a high rate of oil delivery is needed, especially at low engine speeds. Its fundamental principle remains the same: two rotating wheels create oil pressure near the delivery nozzle. The two wheels move in tandem, unlike the opposing wheel movements found in gear and rotary pumps. Because the two wheels differ in size, oil is transported to the delivery nozzle and pressure is generated by progressively shrinking the containment area—or the crescent—that forms between the wheels.
