Atkinson cycle

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The Atkinson cycle in a pv diagram
Atkinson engine: Drawing from U.S. Patent 367496
Animation of the Atkinson engine

The original Atkinson cycle is a cycle in four-stroke engines . It is named after its inventor James Atkinson . The Atkinson engine has different piston strokes and thus different volumes for “suction / compression” and “expansion / discharge”. The crank drive is designed so that the piston moves further down when "expanding" and further up when "ejecting". This leads to more exhaust gas emissions and more exhaust gas expansion. In the original design, an additional rocker arm and another connecting rod are installed between the crankshaft and piston , so that the piston goes up and down twice differently with one crankshaft revolution.

Atkinson invented his machine in 1880 to circumvent the patents of Alphonse Beau de Rochas (1862) and Nikolaus August Otto (1878) by realizing the four-stroke process in one revolution of the crankshaft.

Miller cycle with early closing inlet valve

The Miller cycle (patented in 1947 for Ralph Miller) works in almost the same way , in which the inlet valve closes very early, well before bottom dead center (BDC) and shortens the intake stroke so that bottom dead center is passed through with negative pressure.

Usually it is controlled with a variable valve control, i. H. the filling is controlled by the opening time and stroke of the valve instead of the throttle valve .

Atkinson cycle with late closing inlet valve

Under the Atkinson cycle in modern gasoline engines (now also diesels) is understood as the late closing of the inlet valve well after bottom dead center (BDC), which means that part of the sucked in gas is pumped back before the actual compression begins when the valve closes.

Compared to the Miller cycle, the Atkinson cycle can use the gas dynamics of the intake process. In addition, the Atkinson cycle has a lower degree of delivery in the lower speed range than at high speeds, which is the opposite of the Miller cycle.

Honda EXlink

Honda developed a gas engine in which an additional connecting rod between the housing and a lever rotating with the crankshaft (on which the piston connecting rod is mounted) causes different strokes in the compression and work cycle. With a compression of 12.2: 1, the system has an expansion ratio of 17.6: 1. Honda calls this system "EXlink" (for "Extended Expansion Linkage Engine") and markets it for small combined heat and power plants .

Advantages & disadvantages of the Atkinson engine

The disadvantage of Atkinson's original design is the complicated crank mechanism with poor power transmission, which the common implementations by means of valve control circumvent. The main advantage of the Atkinson process lies in the fact that the gas is further expanded and cooled down by the extended expansion stroke, so that the energy contained in the gas is better utilized; the thermal efficiency is higher. The discharge pressure and the discharge temperature and the maximum combustion pressure and the maximum combustion temperature are the same as the conventional gasoline engine , the Atkinson engine higher efficiency provides for low capacity: The intake volume , which is critical to the performance, is smaller than the expansion volume which is decisive for the efficiency. To compensate for the lower output, the displacement is usually increased and / or the engine is charged and the charge air is cooled .

Atkinson hybrid drive

The combination with an electric motor ( hybrid drive ) is ideal , for example in the Toyota Prius , Ford C-Max Energi , Mercedes S400 Hybrid , Mitsubishi Outlander Plug-in Hybrid. In particular, the reduced dynamics when accelerating can be compensated for by an electric motor.

Individual evidence

  1. ↑ Patent US367496 : Gas Engine. Filed October 18, 1880 , published August 2, 1887 , inventor: J. Atkinson. ‌
  2. ↑ MTZ 01/2017, " Turbocharger with variable turbine geometry for Miller gasoline engines ", pp. 44–49, ISSN  0024-8525 10814.
  3. ↑ a b c Konrad Reif (ed.), " Gasoline engine management at a glance ", Springer Fachmedien Wiesbaden 2015, section "Cylinder filling", ISBN 978-3-658-09523-9 .
  4. ↑ a b Richard van Basshuysen, Fred Schäfer (Ed.), " Handbuch Internal Combustion Engine", 8th revised edition, Springer Fachmedien Wiesbaden GmbH 2017, section 7.10.1.5 "Variable valve drives", ISBN 978-3-658-10901-1 .
  5. ↑ a b MTZ 06/2016 " The new six-cylinder marine engine from MAN for yachts and work boats ", pp. 50–55, ISSN  0024-8525 10814.
  6. ↑ http://world.honda.com/powerproducts-technology/exlink
  7. ↑ Stefan Pischinger, Ulrich Seiffert (ed.), " Vieweg Handbook Motor Vehicle Technology ", 8th edition, Springer Fachmedien Wiesbaden 2016, section 4.3 "Novel drives", ISBN 978-3-658-09527-7 .

Web links

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