Variable Duration Camshaft or Helical Camshaft.
This invention (usually referred to as the "Helical Camshaft") allows a conventional four-stroke engine to be able to vary the duration of its valve opening over a very wide and continuous (that is; stepless) range.The system is totally mechanical (that is; not "camless" - solenoid or electro-hydraulic). The range of variation is all at full valve lift - the lift remaining constant; the opening and closing rates of valve velocity, acceleration, jerk etc. are unchanged no matter what the overall duration is. These rates of valve velocity, acceleration etc. are basically identical to those of a conventional camshaft.
The camshaft, in concept, essentially replaces a conventional camshaft - the system operating through conventional lifters. Only a very short axial movement of part of the camshaft is needed to vary the duration. For example, in the running prototype test engine, one inch (25mm) of movement gives a change in duration of 85 (crankshaft) degrees. In theory a duration variation of up to 720 degrees is possible. Even at this hypothetical extreme the rates of valve opening/closing remain unchanged.
This wide range of duration variation is not only enough to allow maximum engine "breathing" for any possible extreme RPM but is also enough to allow throttle-free load control of the engine by Late Inlet Valve Closing (LIVC). Load control by LIVC promises fuel savings due to the reduction of "pumping losses".
Fuel useage trials on the prototype camshaft and engine have displayed very high savings of up to 40% at idle RPM. These savings reduce progressively with increasing engine load/increasing manifold pressure until they disappear entirely at wide open throttle conditions. However, on the road in real life stop-and-start traffic conditions, this still would probably equate to fuel savings of between 10% and 20% overall.
The aim of a mechanical camshaft system that will allow wide-range stepless variation at full lift of the valve opening duration has been for a very long time an unfulfilled ambition and "Holy Grail" of the automotive world. It is also the perfect "magical" camshaft system that almost every performance car enthuiast has been waiting for. Surprisingly, such a camshaft system has never been achieved in the very long history of the internal combustion engine despite the untold efforts of thousands of engineers and vast amounts of money spent by car companies, research organisations and private inventors. The Helical Camshaft is the only mechanical system of varying the duration of valve opening in such a desirable fashion that has ever existed, and, quite possibly, the only such system that will ever exist.
The Helical Camshaft system has been the subject of many magazine articles and has been scrutinised by professional company engineers - all agree that is does indeed perform as described above and may well be the long sought-after "Holy Grail".
Patents:
US 6,832,586 issued 2004-12-21 [MORE INFO]
Type of Offer: Sale or Licensing
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