Adding a balance weight to a hollow camshaft isn’t a completely new idea, but Subaru has found an innovative strategy.
The idea for the first camshaft, it’s said, dates all the way back to Mesopotamia, where it was found in inventor Ismail al-Jazari’s writings from 1206. Now, 800 years later, engineers are still hard at work on improving it. Case in point: Subaru has filed a new patent for a hollow camshaft with a lockable balance weight meant to reduce vibrations.
"Restraining the resonation” is how patent lawyers say it, but if this technology makes it to production, we’re sure it’ll be referred to as “smooth.”
The lowly camshaft might still hold some engineering secrets. A new patent from Subaru reveals a hollow camshaft concept that could reduce an engine’s operating vibration thanks to a restrained balance weight.
The patent, first spotted by CarBuzz, evolves the camshaft—at its most basic level, a rod in the engine with bumpy cams on it that help control when a valve opens or closes—by making it hollow and adding a balance weight that locks and unlocks its position relative to the shaft depending on the engine’s speed.
Today, hollow camshafts are often used in racing engines to provide important, if minimal, weight savings, and most “solid” camshafts have an oil passage inside for lubrication purposes. What the eight Subaru engineers named on the patent are talking about here is having a balance weight, a specially machined smaller hollow cylinder, inserted into the shaft to reduce vibrations caused by the exterior cams.
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