As market and government regulations require automakers to improve emissions and fuel consumption, they are evaluating all opportunities in engine systems to reduce losses. The oil pump is an important component that consumes engine power because it protects engine components from friction and wear and overheating by delivering engine oil at the correct pressure.

Fixed displacement oil pumps currently circulate oil in most cars. Designers often increase the size of the pump to handle the most demanding engine operating conditions. In most cases, they consume more power and provide much more oil pressure than required. They include pressure reducing valves, a rough, cost-effective and reliable way to avoid excessive oil pressure. However, these designs are inefficient, and a large amount of energy is lost at the high oil flow typical of internal combustion engines.

Provide customized oil flow
Variable displacement oil pumps help minimize energy loss. Their active control matches the oil flow and pressure required by the engine, eliminating excess oil flow, significantly reducing parasitic loads on the engine's crankshaft, and ultimately saving fuel.

In variable displacement pumps, changing the displacement can control the flow. Vane pump designs have hydraulic and electrical controls and actuators that move the pump casing and change the eccentricity of the rotor. Electronic control signals and solenoid control valves change the pressure setpoint based on operating conditions.



Benefits of reduced traffic
The variable displacement pump can customize the oil pressure down to 1-2 bar, which has a larger range than the standard fixed displacement pump's 4-6 bar. They can also provide lower flow rates. This combination greatly reduces the energy consumed by the pump, thereby improving fuel economy by 3 to 6% during both hot and cold starts, and higher engine speeds yield greater fuel economy advantages.

Reducing parasitic energy losses at low flows is only part of the equation. Controlling fuel supply pressure also brings more benefits in the engine. The chain tensioner's hydraulic tensioner is affected by the supply pressure. Keeping the pressure low will reduce the operating tension in the chain drive and its parasitic losses.

During the warm-up period, the more efficient pump heats the oil less and reduces the temperature of the oil produced by 4 ° C. Less heat is generated in the pressure reducing valve and less total heat is transferred to the oil around the engine piston and cylinder bore area.

Controlled heat penalty
The reduced fuel flow improves fuel economy, while also increasing the temperature of the combustion chamber and reducing the cooling of the pistons, thereby heating the metal cylinder liner from 2 ° C to 6 ° C. This effect reduced hydrocarbon and carbon dioxide emissions by 3 to 5%, but also increased NOx by up to 3%.

Intake, combustion chamber, combustion temperature, and engine load all greatly affect NOx. "Usually, reducing engine load reduces NOx, but as the oil flow decreases, the piston becomes slightly warmer, which increases NOx, so we are usually neutral. During normal warm-up driving, NOx is negligible. In a hot engine, although the NOx is small, it can be easily affected by changing the intake air temperature by a few degrees.

The variable flow pump wins in terms of fuel economy and has a small effect on NOx because it does not significantly affect the combustion temperature. "As with all active systems on internal combustion engines, calibration addresses this compromise.


Potential for widespread use
Compared with other control mechanisms such as EGR or injection timing, this method has lower NOx loss and is very beneficial to fuel economy. "All vehicles can benefit from this technology because it is inexpensive and universally applicable. The advantages of variable flow oil pumps are directly related to the engine's operating speed, with higher speeds being the most beneficial," he said.

On fixed-speed displacement devices, the biggest disadvantage of a small engine (such as an engine in a car) running over a large speed range is the biggest benefit. However, this is still a cost-effective improvement in applications over a wide range of operating speeds and temperatures.

Any technology that reduces friction will bring benefits in all engine operating conditions. Fuel economy improvements that reduce fuel consumption are more cost-effective in terms of revenue per dollar than options that rely on the drive cycle, such as hybrids, and hybrids gain more during cold starts and stops Efficiency gains, and less gain on highways Peg says that every 1% increase in fuel economy can cost hundreds of dollars, while the installation of variable-flow oil pumps increases 3 %, It will cost tens of dollars.

These types of pumps are gradually entering many markets. Variable flow oil pumps will become a normal business.

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