An interesting patent has been filed by Toyota for an engine with variable compression.
The patent is for an engine with variable length connecting rods. The connecting rod features two hydraulic cylinders at the top, which use a check valve, switch pin and hydraulic oil to determine which cylinder is compressed. One of the cylinders enables a lower compression ratio, while the other is for a higher compression. When the engine’s oil pressure is at a certain level, the longer high compression connecting rod would be actuated, while the lower compression rod would come into play when the oil pressure is lower.
Such a design helps to prove the best of both worlds when it comes to engine performance. The low compression setting provides maximum fuel economy during leisurely drives or commutes, while the high compression setting would come into play when the driver wants more performance. This isn’t the first time an automaker has looked at variable compression engines. Last year, Nissan and Infiniti highlighted a variable compression four-cylinder engine that would use a piston rod on a type of multi-link hinge that could change the angle of the connecting rod, thus changing the stroke of the piston. Nissan’s design also featured a turbocharger for additional efficiency and performance gains.
Toyota hasn’t said if this design could be used in a four-cylinder, V6 or V8 engine, however, it was assumed that Nissan’s design would work best with a four-cylinder in order to cut back on costs and engine complexity. It’s also not clear if Toyota is seriously considering producing such an engine, or if it would simply like to research such technologies as it looks to make gains in fuel economy with standard internal combustion engine vehicles.
View the entire patent, complete with plenty of diagrams, at this link.
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