Automotive Design Interview
the extent that cylinders would be deactivated on a real time basis.
Eliminating loss But one of the obvious and immediate fuel saving benefits – 3.5-6%, according to Stone – would be the elimination of the throttle and its associated pumping losses. “The other great thing is that, whatever the engine load/speed condition is, you don’t have some timing and lift compromise; you have the valve timing, period and lift for that particular event. Our research suggests this will result in an overall FE improvement of more than 15% - both on the statutory cycle and in a real world driving environment. “In the 70s, before
cam phasers started to become more common, the valve timing you had at idle was the same as at maximum revs, whereas at idle you want almost no overlap and at full engine speed you might want 50, 60, 70 degrees overlap. We can do that and, of course, at idle, if only 0.2mm of inlet lift is needed, we can also deliver that.” The key enabler to Camcon’s IVA is a development of its proprietary Binary Actuation Technology (BAT) invented in the late 90s by Wladyslaw Wygnanski, as Stone explains: “Although the IVA employs a desmodromic valve system, that in itself wasn’t the starting point, although the fact that it doesn’t employ a spring, but a cam and leverage system, lends itself to our application by minimising the actuator size and power demand. “The Camcon bi-stable actuator is
a very low energy and fast actuator Unlike a solenoid, it has two zero power stable states, whereas a conventional solenoid has only one, requiring either continuous power or an extra mechanism to latch it. With
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the Camcon binary system, it’s fired from one end to the other, with no latching, and powered only during the switching operation.” This feature, says Stone, makes it
equally applicable to park brake systems, thereby eliminating a potential noise path into the cabin via any cabling. He adds: “The inspirational leap was, ‘Could we make this multi-stable by rolling it into a multi-pole, rather than two-pole device with a rotating permanent magnet arrangement, to drive a poppet valve with it?”
Significant funding “Since 2005, there has been a great deal of Camcon-funded work on the concept and it has been transformed from those early ideas into a sophisticated device, which delivers a real capability greater than any system on the market or, as far as we know, in development.” Unlike some camless
systems seen in the past,
which relied on opposed solenoids to both open and close valves, and on 48volts, Camcon’s runs on a standard 12volt system assisted by an energy recovery system, as Stone explains: “When the energy recovery cam is at full lift, the energy recovery spring has got maximum strain energy, but generates no torque, as long as the cam is on peak lift. The moment the cam is knocked off peak lift, it acts as a lever, converting the spring force into torque, and starts pushing energy into the mechanism. That gives an energy boost, so less electrical power is required. When the valve closes, so the actuator stops each time; not half engine speed or anything like that – its ‘go’, ‘stop’. So every engine cycle/valve cycle, the actuator stops. And, in stopping, kinetic energy is recovered in the spring and recycled next time round.” Effectively there are three cams: a
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pair of desmodromic driven ones to open and close the valves and a third on the same shaft to operate the energy recovery spring. Cost, as ever, is an issue and, as
in so many instances, is dependent on numbers being manufactured. However, Stone suggests that the IVA will come in at “around the equivalent of a diesel injection system of one thousand pounds or euros, or thereabouts”, of which the VCU represents “a big chunk”.
Mix ‘n’ match What this means to the OEM, says Stone, is that they can mix ’n’ match the valve train, according to an engine’s individual requirements: “You could have one actuator per valve or just do the inlets only and have conventional exhausts; or you could tandem them up, so there’s one IVA actuator between a pair of valves. Or, go the whole hog on the inlets, with individual actuators and tandem them on the exhausts. If you have independent control on every valve, you have more flexibility and benefits than if you compromise. “The £1,000 would be at the top
end of the range; if you only spend half that, you don’t quite get half the system, as the VCU will be a significant investment.” Further savings can be made,
depending on the engine’s architecture, claims Stone. “It’s a new head, obviously. In terms of the bottom end, it’s delete really, as we don’t need the timing drive any more, unless you run the exhaust cam; in which case, it’s even simpler: you just delete the inlet sprocket. It depends on the individual design of the engine. If the water pump is driven by the timing chain, it’s a bit more complicated than just deleting the timing drive, but IVA could be retro fitted or run as a derivative, with other more conventional variations of the same engine family alongside each other.” The beauty of the system is that OEMs can tune it to meet their own
May/June 2013
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