One of the biggest drawbacks of single-cylinder engines, especially higher displacement ones is widely agreed to be the vibrations. Until now, companies have mostly stuck to using counter balancer shafts as the preferred way to keep them under check but with QJMotor’s latest patent in the US, we might just have a more interesting and, potentially, more affordable way to deal with them.
- Uses a smaller ‘dummy’ cylinder as a counterweight
- More cost-effective than gear operated counter balancer shafts
Single-cylinder engine with a V-Twin-like configuration
A dummy piston in the second cylinder only cancels out vibrations
Technically speaking, the patent has been filed by QJMotor’s parent firm, Geely Auto Group, and it demonstrates an innovative approach to controlling engine vibrations in a single-cylinder mill. The patent drawing shows an engine crankcase with two cylinder bore holes at an 80 degree angle, visually resembling a V-twin engine. In the patent images, the larger bore on the right contains the actual combustion cylinder with a standard piston performing the four stroke (intake, compression, combustion, and exhaust) action. The dummy cylinder on the left bore has a piston that is connected to the same crankshaft via a connector rod. However, this piston has an air vent, meaning this cylinder does not act as a combustion chamber. It simply moves up and down as a counterweight through the crankshaft’s rotation, canceling out the vibration produced by the ‘real’ cylinder.
Lack of piston rings underlined as the major improvement
Cylinders and the pistons are cleverly offset too
The second piston lacks piston rings since it’s not sealing a combustion chamber, which removes friction and drag. The source also underlines that the presence of the piston rings (and the friction and drag they produced) were the main flaw in earlier attempts at this configuration. Both connecting rods share the same crankpin as well, to minimise the size of the entire assembly.
The cleverer part is that despite the cylinders themselves being angled at 80 degrees, the pistons are angled at 90 degrees. This wider angle is made possible by housing the balancing cylinder in a separate component that’s bolted onto the crankcase with a flange, rather than being machined directly into the block. And because this cylinder offers some clearance against the bore, the piston can travel along its offset path. This allows the effective angle between the two cylinders to be wider than that of the casing itself. Lastly, since the balancer piston has no conventional intake or exhaust valve, it gets cooling fins to reduce heat build up.
The patent details the goal behind the design to achieve a proper balance-shaft system, but at a lower cost and less complex design. The patent was published by the United States Patent and Trademark Office on August 27, and there’s no indication that it’ll make its way onto a production motorcycle anytime soon.
Source: MCN
