Variable crank drive
Crank drives are preferably used in reciprocating internal combustion engines and consist of a crankshaft that moves the pistons up and down in the cylinder of the crankcase via connecting rods.
A variable crank drive can serve several purposes:
- a variable compression ratio (also referred to simply as variable compression ),
- a variable stroke volume ,
- a variable piston stroke curve (more precisely: alternating piston stroke curve ), e.g. B. by articulated connecting rods .
The goal is usually to increase the thermodynamic efficiency of a reciprocating engine. The basic idea comes from the development of the internal combustion engine, the late 19th century. Despite considerable potential for savings in fuel consumption, variable crankshaft drives have not yet been used in vehicle drives, since technologies that could be implemented more easily were available to reduce fuel consumption in internal combustion engines, e.g. B. exhaust gas turbocharging , variable valve train (camshaft phaser and control of valve lift) and thermal management systems (to improve efficiency, especially when the engine is warming up). In vehicle drives, the variable compression ratio offers the highest potential of approx. 9% compared to an already highly developed, supercharged gasoline engine with direct injection.
Since the implementation of engines with variable compression requires high investments, it is questionable whether the vehicle manufacturers will not concentrate instead on the electrification of the drive train.
The only commercial series application of a variable crank drive is a single-cylinder small engine with 163 cm³ expansion stroke volume (1 kW mechanical and 2.5 kW thermal power), which was jointly developed by Honda Motor Co. Ltd. in 2011. and the Vaillant Group. This motor with an alternating piston stroke is used under the designation "Extended Expansion Linkage Engine" (Exlink) in micro-block thermal power stations for single-family houses.
Individual evidence
- ↑ a b Matthias Brendel: Realization of a variable crank drive for a supercharged gasoline engine. 1st edition. Cuvillier Verlag, Göttingen 2013.
- ↑ G. Fraidl, P. Kapus et al.: Variable compression - in technology competition? In: International Vienna Motor Symposium. Vienna 2016.
- ↑ Anonymous: Data and facts about the micro-heating power plant ecoPOWER 1.0. (Press material). Vaillant Group, Remscheid 2011.
- ^ J. Yamaguchi: Back to the Future - The Way of Honda. In: Automotive Engineering. Volume 119-6, 2011, pp. 22-25.