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This is an idea I've had for a while, we all know about variable valve lift but only few car manufacturers seem to have adpted this mainly because of costs so I propose the use of cambered cams. I don't know if this would increase production costs, but the surface of the cam that touches the valve would
slant to one side. At first I thought of using a telescopic camshaft that allows the camshaft to slide over cambered roller cam followers but this idea was scraped. The one I'm suggesting goes as follows; imagine a roller cam follower connecting the two valves for the intake, one side is spring loaded and the other is an inlet that allows for oil, the pivot rod on which the cam followers are attached is made hollow for oil passage to the cam followers. If every cylinder has this set-up then if a hydraulic pump is uesd to force oil into the cam followers so that they slide, then their surface orientation with the cambered cams can be varied thus allowing for continous control of lift.
How Stuff Works: Honda's VTEC system
http://auto.howstuf...vtec/whatsvtec.html
Honda's variable valve control implementation, explained with pretty pictures. [ed, Nov 23 2004]
Just A Picture I Drew
https://plus.google...5707269670977263922
Link to a photo of a simple picture of how I think this camshaft would work. Sorry about the sidewaysness, google scales pictures in a dumb way. [BuffMyRadius, Feb 09 2012, last modified Feb 10 2012]
[link]
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2.//we all know about variable valve lift//... uh...uh.. link? |
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I know a little (a very little) about variable valve timing, but I think just enough to understand what you are proposing. Basically, each cam roller has one side slightly in advance of the other, so by sliding the camshaft lengthways you adjust the timing, right? I totally don't understand the oil pump bit, but I'm hoping that's not intrinsic to the idea. Sounds like a neat solution, you get a croissant. Welcome to the HB. |
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Added link describing Honda's implementation of variable valve control: multiple lobes, for those without knowledge of VVC. |
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Could you provide a pic/cad drawing of your cambered cams idea? Sounds nifty. Pastry. |
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How about having two cam-shafts which rotate with a variable phase delay between them; one of them operates the exhaust valves and opens the intake valves which then latch; the other camshaft trips the latches on the intake valves. Since the primary benefit of variable valve timing is adjustable delayed intake closure (there's no reason not to open intake at any time other than exhaust->intake TDC, nor to open exhaust at any time other than power->exhaust BDC, nor close it at any time other than exhaust->intake TDC just before intake opens. But delaying closure of the intake valve will improve efficiency while reducing power. |
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The same thought just struck me and the thought "has someone on halfbakery thought of this yet?" came to mind directly. I get exactly what you are saying about the cam lifter. The head that rides on the cam would have to adjust to differing angles as it rides across the cam. The main issue that I see is that the cam profile would have to have a linear change at a set point along it's rotation, otherwise the flat surface of the lifter would be making contact on a laterally curved surface, which would cause lots of wear. I have never used a CAD program, but I think I will take a stab at a drawing. |
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[BuffMyRadius]: Could you fix the link? It just seems to put up a generic Google Plus page. |
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