PATTAKON
GREECE
Continuously
Variable Valve Actuation system.
Provides a continuous range of valve lifts, from zero to maximum.
It is
simple, reliable, light, short, efficient and capable for really high revs.
There is no
need for any additional spring (the normal valve springs proved, in practice,
adequate for the entire train).
There is no
need of any electromotor to rotate the Control Shaft(s), i.e. no need for
"drive by wire". The only "wire" involved is the string previously rotating the
throttle valve, which now is employed to rotate the Control Shaft(s), and this
is all.
Easy in
assembly, involves a mere couple of components per valve (actually one and a
"half"), plus a control shaft per row of valves.
Patent Data
International Publication Number : WO 02/103169 A1 (27 December 2002)
International Application Number :
PCT/GR02/00035 (14 June 2002)
Priority Data : 20010100295 (18 June 2001 GR)
The complete Patent (Description, Claims,
Drawings, Abstract) and the International Search Report can be found at
WIPO/PCT site.
The angular
position of the control shaft defines the lift of the relevant row of valves.
The
camshaft acts on the valve by means of
a control lever swiveling on the control shaft,
and
a valve lever (just a needle) swiveling on both, control lever and valve actuator (bucket lifter or rocker arm or valve stem or …).
The system
controls independently intake and exhaust valves, changing the valve lift while
keeping unchanged the valve clearance.
Unlike the
typical Variable Valve Timing ( VVT ) systems which control the angular overlap
at TDC but spoil relatively the status
around BDC, the Variable Valve Actuation system ( VVA ) changes not the angular
(typical) but the actual overlap at TDC (namely, the "time-valve area" when
both intake and exhaust valves are opened together) improving at the same time
the status around BDC.
"Drive by
wire" is simply an option, not a necessity. Some people might prefer a "drive
by wire", even though the mechanism operates as simply as if turning the
throttle valve of the conventional engine.
The
prototype engine (Renault 19 GTS Energy, 1400 cc, 8 Valves, carburetor, not
catalytic, 1989 model) was intended in the first place only to increase fuel
economy and reduce emissions, however in the course of the events it turned out
capable of providing other qualities as well. Besides being much more fuel
efficient and with more than thirty times less Carbon Monoxide in the exhaust
gas at idling (relative to the original engine), it proved itself not only
quite more powerful, which had been anticipated on the grounds of the wilder
camshafts, but surprisingly torquie and reliable, smooth at idling, able to
handle extremely lean mixtures, excellent at partial loads, driver friendly
with unexpectedly immediate response in transient conditions, etc.
The Carbon
Monoxide at idling was officially measured at 0.05% with the engine normally
warmed up. The CO is less than 0.1% with the engine completely cold at
starting. The normal engine had 1.8% CO in exhaust gas, and this only after the
warming up period.
The engine
can effectively handle extreme lean mixtures by making them fine "mincemeat",
that is homogeneous as it should. On the other hand, the response is immediate,
crisp, even with cold engine and without any acceleration pump involved.
The engine
can idle at 350 rpm.
The engine
has been tested repeatedly at only 7000 rpm and full load, because more revs
will damage the conventional parts of the engine (pistons, valves and springs,
connecting rods and crankshaft, as the red starts at 5500 rpm and the dark red
at 6000 rpm).
The torque
at extreme low revs resembles that of a truck, and at high revs that of a
motorcycle.
In the
following the first and unique prototype is outlined and specified. Though it
is actually a hand made mechanism, nevertheless it is surprisingly reliable and
the car is currently used for any task. It was (and still it is) tested for
thousands of kilometers in town traffic (Athens' traffic), open roads and
extreme uphill. The specific engine (with a Weber carburetor and just 2 valves
per cylinder) has been selected simply because it was available at the time.
The intake
and exhaust control shafts, the control levers (the intake are assembled in
their control shaft), and the valve levers (indeed valve needles). Double
bearings on control shafts for keeping the control levers: at right side
complete, at left partial for inserting the relevant control lever. There are
no additional securing means for keeping the control or valve levers in their
position.
The
previous from the opposite side.
The system
schematically at four different control shaft angles (same camshaft angle).
The Control
Lever (stereoscopic representation*).
Case of
four valves per cylinder (stereoscopic representation*).
A part of a
Control Shaft (stereoscopic representation*).
Schematically
the mechanism mounted on Renault 19 Energy engine (stereoscopic
representation*).
Case of straight
four 16 valves (stereoscopic representation*).
*To see stereoscopically the above slides, just hide the left image from your left eye and the right image from your right eye by your palms and then try to concentrate your sight on a small object located at the intersection of the line from your left eye to the right figure and the line from your right eye to the left image. The "software" is already into the brain waiting for activation. The result is stunning.
The
stereoscopically viewed objects are formed in the space in front of observer and
not on the screen.
The moving diamonds ("Diamonds" at the last page of the site)
"leave" the screen and fly in the space, some moments close
to observer and some moments away, behind the screen.
The
deliberate confusion on the last image of this page clears "magically" and
becomes readable only when viewed
stereoscopically.
The system
mounted on the top of a Renault 19 Energy 1400 cc engine (without catalytic
converter). Spot on the control shaft levers and the string at the right side.
The butterfly of the carburetor is locked wide open.
As viewed
from the timing belt side. The green plastic pipe is for crankcase ventilation.
The above
system as a unit located on top of the valves,
and looked
at from the timing belt side, at zero lift.
What the
ideal Variable Valve Actuation system offers are constantly the optimum
and practically the same conditions to the mixture (intake manifold
pressure, swirl, turbulence, scavenging of the cylinder during overlap, velocity
around valve seats, mixture homogeny etc) for entering the cylinder, in order
to get burnt as effectively as it gets, and then scavenge the cylinder at
all revs and every load.
The rule seems general and quite simple: the necessary valve lift is about linearly
proportional to both revs and load.
For the mixture what counts is its
own kinematics and thermodynamics, not the speed of the crankshaft, the
cylinder wall temperature, the load etc.
In an ordinary engine tuned at 6000 rpm and full load
but operating at 1500 rpm and one third of the full load, the entry speed of
the mixture into the cylinder is not 2 or 3, but more than 10 times lower. The
overlap from blessing at 6000 rpm becomes curse at 1500 rpm. Needless to say
more.
The above plot
depicts the original valve lifts of the engine (bold orange for the exhaust and
bold green for the intake valves) and a group of available lift curves with the
VVA system mounted. The vertical axis is the valve lift in mm and the
horizontal the rotation angle of the crankshaft, in degrees. The red curves are
the exhaust valve lifts for 65, 33, 18, 8, 3 and 1 degrees of exhaust control
shaft rotation, while the blue curves are the intake valve lifts. Any red curve
can be combined to any blue. Spot on actual (not simply the conventional
angular) overlap: at high lifts it becomes more than double of the conventional
engine while at low lifts it becomes negligible.
An ordinary
VVT system reduces the overlap at low revs and partial loads, retarding intake
valves opening and closing, and advancing exhaust valves opening and closing.
The retarded intake closing and the advanced exhaust opening are the side
effects, which make the situation around Bottom Dead Center completely wrong,
yet the need for reduction of the overlap at Top Dead Center prevails.
An
intelligent VVT system has to reduce, at partial loads and low revs, the
overlap at Top Dead Center, and at the same time it has to retard the exhaust
valves opening and advance the intake valves closing. It can be done, but it is
complicated and expensive.
A VVT could
of course be combined to the presented system, however, as the Variable Valve
Actuation mechanism controls effectively the actual overlap too (where the term
actual overlap defines collectively the lift - time area) it does not need a
VVT system, at all.
In fact,
the specific VVA system is an intelligent VVT too, since it controls properly
the overlap at Top Dead Center and, at the same time, improves the conditions
around Bottom Dead Center, closing, at low lifts, the intake valves
substantially advanced and opening the exhaust valves substantially retarded
(even if a valve is completely closed at a specific angle, it is in fact almost
closed during many degrees before that typical closing, i.e. when the instant
lift of the valve becomes adequately short).
The
operation further improves thanks to the substantially constant pressure in
intake manifold. As there is no vacuum in intake manifold to pull back
(suction) the gases from cylinder and exhaust, the quality of the mixture
becomes more controllable resulting in lower emissions, larger allowable
overlap and enhanced quality of operation.
Applying this Variable Valve Actuation System
the behavior of all engines (racing or ordinary)
can be improved at all revs:
·
the engine can idle at very low
revs steadily, with low noise, vibrations, consumption and emissions,
·
the
engine can produce, roughly speaking, constant torque at all revs, from extreme
low to extreme high,
·
the
engine's response becomes instantaneous, immediate, and crisp,
·
the
engine can work perfectly at partial loads,
·
the
valve train's expected life becomes significantly longer,
·
the
engine can efficiently burn lean mixtures,
·
the
consumption and the emissions can be drastically reduced, in particular at low
to medium revs, and finally,
·
the
engine can deliver even more power at high revs using wilder camshafts, simply
because the Variable Valve Lift System provides the drivability and
friendliness at all revs and loads (the wildness of the camshafts show up only
at maximum lifts).
The lightweight of the constituent parts, the
diminished internal friction and the "as it should be" loading make the system
suitable for most kinds of services, from lorries to racing.
Once
mastered the mechanism, it becomes obvious that:
It is simple in operation and manufacturing, made up of very few parts.
There are no wear concentration or stress
concentration points. Absolutely none.
The inertia loads from the reciprocating (or oscillating)
parts are very low (lower than the loads, in the valve train of the
conventional engine, produced from the replaced parts, i.e. bucket lifters or
rocker arms).
The swivel joints -valve lever to control
lever, valve lever to valve adjuster and control lever to control shaft- are
mechanically correct, simply because there is surface contact (and not line or
point contact which reduce the expected life and make inevitable often
adjustments).
The valve adjuster pushes the valve stem only
along the valve guide direction, so the valve guide can long live.
The valve adjuster slides along a
"hole/slider". At high lifts the thrust force is negligible as the valve needle
reciprocates nearly parallel to the "hole/slider" axis. At low lifts the thrust
is small partly because the inertia loads are small, partly thanks to the
only-partially compressed valve spring, and partly due to the small angle
between valve needle and "hole/slider" axis.
As typical engines operate most of their life
at partial loads and low to medium revs (i.e. calling only for low to medium
valve lifts) the mechanical friction falls and the expected life of the valve
train system becomes much longer than conventional, where the strength of the
valve springs -necessary to return the valves to their seats at maximum revs-
loads excessively everything (cam lobes, cam followers, valves, valve guides,
valve seats, timing belt) at all revs and loads, even at idling.
The
mechanism is simpler in manufacturing and operation than "two step" systems
offered nowadays from car industries (valve deactivation systems included), as
it has no need for tinny pins and holes, as it does not necessitates
complicated camshafts with many cam lobes, as it has no need for even a single
additional spring and involves absolutely no hydraulic system, piping, pumps
etc. Despite its simplicity it offers not only two, but infinite lifts,
starting from zero.
On the
other hand, compared to the "continuous variable valve lift" systems known
today (which are the real competitors) in terms of:
simplicity,
number of parts involved,
number of interfering joints conveying the
motion from cam lobe (or eccentric pin) to valve stem,
necessary accuracy of constituent parts (to
allow the manufacturing even in ordinary machine-shop),
wear concentration points,
additional inertia loads and friction,
expected life,
easy of control,
control on both, intake and exhaust valve
lifts,
applicability on both, new and existing
engines,
completeness, i.e. ability to work without
supporting mechanisms (like "variable valve timing", special controllers, etc),
applicability on all engines, from cheap single
cylinder, to luxury multicylinder, to racing,
effective manipulation of all loads (full load
included) from extreme low revs,
ability for really high revs, in order to make
full use of the theoretical VVA's advantage, i.e. improved behavior from
extreme low revs to the limit imposed only by the strength of the underneath
power train (pistons, connecting rods, crankshaft),
the system
seems to stand in a class of its own.
Even if
still the engines, the valves, the lifts and the similar are "Greeks" to you,
in so far you simply succeeded to see stereoscopically the stereo figures, you
got the very best.
At your
service for any questions.
Thank you
for your time.
PATTAKON
Fax and Tel
No: +30 210 4934402
Post address : Lampraki 356, 18452
GR
Nikea Piraeus