U.S. patent application number 12/717947 was filed with the patent office on 2011-09-08 for duration extender variable valve actuation.
Invention is credited to Emmanouel Pattakos, John Pattakos, Manousos Pattakos.
Application Number | 20110214633 12/717947 |
Document ID | / |
Family ID | 44530212 |
Filed Date | 2011-09-08 |
United States Patent
Application |
20110214633 |
Kind Code |
A1 |
Pattakos; Manousos ; et
al. |
September 8, 2011 |
DURATION EXTENDER VARIABLE VALVE ACTUATION
Abstract
A hydro-mechanical variable valve actuation (or VVA) system that
controllably extends the valve duration. The valve opens up to its
maximum lift mechanically/conventionally. The hydraulic part of the
system controllably retards the closing of the valve, and takes
part only during the valve-closing phase.
Inventors: |
Pattakos; Manousos; (Nikea
Piraeus, GR) ; Pattakos; John; (Nikea Piraeus,
GR) ; Pattakos; Emmanouel; (Nikea Piraeus,
GR) |
Family ID: |
44530212 |
Appl. No.: |
12/717947 |
Filed: |
March 4, 2010 |
Current U.S.
Class: |
123/90.17 |
Current CPC
Class: |
F01L 1/34 20130101 |
Class at
Publication: |
123/90.17 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Claims
1. A variable valve actuation system comprising at least: a
camshaft (1); a cam (2) mounted on said camshaft (1), said cam (2)
having an opening contour (3) and a closing contour (4); a valve
(5); a cam-follower valve-actuator assembly (6), said cam (2), said
valve (5) and said cam-follower valve-actuator assembly (6)
translate the opening contour (3) into a theoretical opening valve
lift pattern (7) and the closing contour (4) into a theoretical
closing valve lift pattern (8); a valve spring (9) for restoring
said valve (5); an oil-chamber (10) having a release-valve (11); a
plunger (12) slidably fitted into said oil-chamber (10), said
plunger (12) being linked or embodied to said cam-follower
valve-actuator assembly (6); a control unit (13) for controlling
said release-valve (11), characterized in that: the valve opens
following substantially the theoretical opening valve lift pattern;
the plunger, pressed by oil trapped into the oil-chamber, retards
the restoring of the valve so that the valve closes controllably
retarded relative to the theoretical closing valve lift pattern,
according the state of the release-valve.
2. A variable valve actuation system according claim 1
characterized in that during the valve closing, the plunger
progressively covers an opening of the oil-chamber through which
oil escapes, so that the damping action of the oil increases, so
that the valve closes smoothly, quietly, without bouncing and in
time.
3. A variable valve actuation system according claim 1 wherein the
oil pressure into the oil-chamber during the valve closing is
substantially higher than the oil pressure into the oil-chamber
during the valve opening.
4. A variable valve actuation system according claim 1 wherein the
release-valve is an on-off solenoid valve electronically
controlled.
5. A variable valve actuation system according claim 1 wherein the
release-valve is an analog valve.
6. A variable valve actuation system according claim 1 that retards
the closing of the valve so that to maintain it open after the
bottom dead center until the unnecessary part of the charge that
has entered into the cylinder is pushed out by the piston, so that
the engine operates controllably at the desirable load.
7. A variable valve actuation system according claim 1 that
controls the breathing of a variable compression ratio engine in
order to provide a substantially variable capacity engine, thereby
an engine capable to operate permanently at optimum thermal
efficiency.
8. A variable valve actuation system comprising at least: a valve;
a cam dictating a basic restoring pattern for said valve to follow
during valve closing; a hydraulic means resisting to the closing
motion of said valve; an on-off solenoid valve, said hydraulic
means applying a strong or a weak resistance to the closing motion
of said valve according the state of said on-off solenoid valve, so
that by controlling the timing of the on-off solenoid valve the
actual restoring pattern of the valve extends controllably beyond
the basic restoring pattern.
9. A variable valve actuation system according claim 8 wherein for
the smooth landing of the valve on a valve seat, the hydraulic
means comprises means that substantially increase its damping
action as the valve approaches the valve seat.
10. A variable valve actuation system comprising at least: a cam
having an opening contour and a closing contour; a valve; a
cam-follower valve-actuator assembly for displacing said valve
under the camming action of said cam; said cam, said valve and said
cam-follower valve-actuator assembly translate said opening contour
into a theoretical opening valve lift pattern and said closing
contour into a theoretical closing valve lift pattern; an
oil-chamber having a controllable release-valve; a plunger slidably
fitted to said oil-chamber, said plunger pressed by the oil trapped
into said oil-chamber retards the valve closing, the valve opening
substantially follows the theoretical valve lift pattern, whereas
the actual valve closing pattern envelopes the theoretical closing
pattern, so that the valve duration is controllably extended.
Description
[0001] This invention relates to a hydro-mechanical variable valve
actuation (or VVA) system that controllably extends the valve
duration.
[0002] FIG. 1 shows the valve lift versus the time, for the
operation of an engine at 1000 rpm and at 5000 rpm.
[0003] FIG. 2 shows the valve lift versus the time for the case of
heavy load at 1000 rpm.
[0004] FIG. 3 shows the valve lift versus the time for medium load
at 1000 rpm.
[0005] FIG. 4 shows the valve lift versus the time for light load
at 1000 rpm.
[0006] FIG. 5 shows the valve lift versus the time for idling at
1000 rpm.
[0007] FIG. 6 shows the valve lift versus the time for various
loads at 5000 rpm. In FIGS. 2 to 6 it is marked by dashed line the
valve lift for the case where the hydraulic system is disengaged
and the valve closing is controlled by the cam.
[0008] FIG. 7 shows the basic mechanism in the case of roller
finger follower valve train with hydraulic lash adjusters. The
parts are sliced to show the details.
[0009] FIG. 8 shows what FIG. 7 with the parts not sliced.
[0010] FIG. 9 shows the mechanism of FIG. 7 from various viewpoints
and exploded.
[0011] FIG. 10 shows the basic mechanism in the case of a valve
train with bucket lifters.
[0012] FIG. 11 shows more details of the mechanism of FIG. 10.
[0013] FIG. 12 shows the basic mechanism applied on a side cam Vee
engine.
[0014] FIG. 13 shows a modification of the mechanism of FIG.
10.
[0015] FIG. 14 shows the operation principle as compared to the
prior art, at right.
[0016] The closest prior art is the multiair system of Fiat, U.S.
Pat. No. 6,918,364, a lost motion hydro-mechanical VVA currently in
mass production, wherein a cam opens the valve indirectly by means
of a fluid interposed "in series" between the valve and the cam:
the cam by a plunger displaces the fluid, and the fluid displaces
the valve. A solenoid valve is opened the right moment allowing the
fluid to escape and the valve to close, reducing either the
duration or the duration and the lift. The inherent elasticity and
play of the "hydraulic" system, the high loads it undergoes, the
sensitivity to leakage, the need of additional means for the smooth
landing of the valves, the need for additional restoring springs
are some of the problems of the prior art.
[0017] In the present invention the valve opens up
mechanically/conventionally to the maximum lift, under the action
of a cam of a camshaft. The hydraulic part of the system
controllably retards the closing of the valve, and takes part only
during the valve-closing. The opening of the valve causes the
displacement of a plunger slidably fitted into an oil-chamber. Oil
enters into the oil-chamber through a one-way-valve or other type
of valve. During the valve closing, the pressure of the oil into
the oil-chamber increases. The trapped oil reacts to the force from
the valve spring to the valve and to the plunger, disengaging the
valve from the cam. The valve closes later, under the restoring
action of the valve spring, dew to the damping action of the oil
escaping out of the oil-chamber. A release-valve, for instance a
solenoid on-off valve, opens at the right moment (i.e. at the right
crank angle) to allow the quick escape of oil from the oil-chamber.
With the release-valve open, the valve restores quickly under the
action of the valve spring, pressing the oil out the oil-chamber.
The conventional lubrication system is adequate to feed the oil
chamber with oil.
[0018] For the smooth "landing" of the valve on the valve seat, the
damping action of the oil escaping from the oil-chamber increases a
little before the landing of the valve, as much as necessary; for
instance by the progressive covering of the discharge port by the
plunger. The shape of the discharge port can be properly designed
to match with the desirable landing characteristics (acceleration,
jerk etc) and to compensate for fabrication etc inaccuracies. I.e.
the system has a simple and effective built-in ability to smooth
out the landing of the valve.
[0019] The valve duration is equal or longer than the duration
defined by the cam. With a cam having 220 degrees duration, the
actual duration of the valve opening can be anything over 220
degrees, i.e. the system controllably extends the valve duration
without effecting the valve lift.
[0020] With reference to FIG. 13: a cam (2), mounted on a camshaft
(1), has an opening contour (3) and a closing contour (4); the cam
(2), the valve (5) and the cam-follower valve actuator assembly (6)
translate the opening contour (3) into a theoretical opening valve
lift pattern (7) and the closing contour (4) into a theoretical
closing valve lift pattern (8); a valve spring (9) restores the
valve (5); an oil-chamber (10) has a release-valve (11); a plunger
(12) is slidably fitted into said oil-chamber (10); the plunger
(12) seals said oil-chamber (10); the plunger (12) is embodied to
the cam-follower valve-actuator assembly (6); the plunger (12)
under the pressure inside the oil-chamber (10) retards the
restoring motion of the valve according a control unit (13) that
controls the release-valve (11); the valve opens following
substantially the theoretical opening valve lift pattern and closes
substantially retarded relative to the theoretical closing valve
lift pattern, under the control of the release valve.
[0021] The system enables the engine to get rid of the conventional
throttle valve.
[0022] The breathing of the engine depends on the timing of the
release-valve, i.e. on the duration of the suction cycle. The
suction cycle starts at the moment the intake valves of the
cylinder open and ends at the moment the intake valves of the
cylinder close, where the actual compression begins.
[0023] An early actuation of the release-valve, for instance 50
degrees after BDC, increases the quantity of air trapped into the
cylinder. A late actuation of the release-valve, for instance 140
degrees after BDC, allows a part of the air originally suctioned
into the cylinder to return back to the intake manifold, thereby
reducing the pumping loss. The increased turbulence and swirl of
the charge entering and leaving the cylinder enables faster,
cleaner and more efficient combustion.
[0024] For example, the suction cycle can continue until 140
degrees after BDC enabling the engine to idle at 600 rpm. This is
because most of the charge suctioned into the cylinder through the
wide open intake valves is pushed out of the cylinder as the piston
moves towards the TDC with the intake valves still open. The
duration of the suction cycle is the key parameter for the control
of the engine. With the suction cycle ending earlier, for instance
at 90 degrees after BDC, a good part of the working medium is
trapped into the cylinder and the engine operates at medium load.
With the suction cycle ending even earlier, for instance at 30
degrees after BDC at 2000 rpm or at 70 degrees after BDC at 7000
rpm, the engine makes its peak torque at the specific revs.
[0025] The same system is applicable on the exhaust valves, too, if
desirable. The cam opens the exhaust valve in the conventional way,
while the oil-chamber with the release-valve control the closing of
the valve. Because of the heavy forces during the opening of the
exhaust valve, dew to the pressure into the cylinder, most of the
state-of-the-art VVAs (mechanical, electromagnetic, hydraulic etc)
avoid or fail to deal with the exhaust valves, limiting themselves
exclusively to the intake valves. The present hydro-mechanical
system, which is not sensitive to leakage, can control the exhaust
valves too, because its "hydraulic" part deals exclusively with the
control of the valve closing, thereby the strong force necessary to
start opening the exhaust valve does not act on the hydraulic
system.
[0026] The ECU (electronic control unit) of the engine triggers
each release-valve independently. Without a signal from the ECU,
the release-valve stays open allowing the oil to escape quickly
from the oil-chamber, i.e. the default or "safety" mode for a
release-valve is "open". This protects the engine in case of ECU
(or other) failure: the system operates in the pure mechanical way,
with the cam controlling not only the opening but also the closing
of the valves. Each release-valve receives a pulse from the ECU.
The release-valve closes at the beginning of the pulse and stays
closed till the end of the pulse. In the simplest case, the ECU
generates, per release-valve and per two rotations of the
crankshaft, a pair of time values T1 and T2 and feeds the
release-valve with a pulse starting at T1 and ending at T2. The
independent control of each release-valve by the ECU allows a
simpler, yet precise and effective control over the engine. Even in
case there are differences from cylinder to cylinder (for instance
because of a different flow capacity of the release-valves or
because of a poor valve lash adjustment) the engine can still
operate clean and smooth because the ECU aligns independently,
based on the feedback it receives, the pulses to the
release-valves.
[0027] Instead of fighting with the accuracy of the constituent
parts, the ECU has the potential to rectify the operation. The old,
difficult and expensive mechanical control turns to an easy and
cheap digital control.
[0028] With the system proposed, an engine can operate either
according the over-expansion Atkinson/Miller cycle for economy/low
emissions, or it can operate according the conventional cycle for
high specific torque. When combined with a Variable Compression
Ratio system, like those disclosed in the U.S. Ser. No. 12/553,975,
U.S. Ser. No. 12/546,714 and U.S. Ser. No. 12/404,355, the overall
result is an actually variable capacity engine capable to
constantly operate at optimum thermodynamic efficiency.
[0029] Applied on a Diesel engine, this system enhances the
volumetric efficiency when it is advantageous, controls the actual
compression ratio, controls the overlap by the retardation of the
exhaust valve closing, enables the controllable exhaust gas
recirculation, etc.
[0030] In a first preferred embodiment, FIGS. 7 to 9, the roller
finger follower, under the camming action of the cam, pushes the
valve to open; the roller finger follower is linked to a plunger by
a pair of rods; the plunger is slidably fitted into an oil-chamber
located beside the hydraulic lash adjuster; oil through a
one-way-ball-valve fills the oil-chamber; when the valve starts
restoring, the plunger into the oil-chamber moves upwards and
presses the oil that has no way to escape; the oil pressure into
the oil-chamber increases and the valve is disengaged from the cam
(FIG. 7, third from left); the valve closes slowly under the
restoring action of the valve spring and the leakage from the
oil-chamber; the right moment the ECU sends a pulse to the
release-valve to open, allowing the quick restoring of the valve
under the action of the valve spring; as the valve approaches the
valve seat, the passage of the oil decreases, because the plunger
progressively covers the opening through which the oil escapes out
of the oil-chamber, and the landing of the valve is smooth. In the
state-of-the-art they are described other ways for the smooth
landing of the valve.
[0031] In a second preferred embodiment, FIGS. 10 and 11, the
oil-chamber is formed between a narrowing of the bucket lifter and
the cover/guide of the bucket lifter; the plunger is embodied to
the bucket lifter; the small cylinder inside the bucket lifter is
the lash adjuster (either mechanical or hydraulic); the bucket
lifter with the plunger and the valve lash adjuster constitute the
cam-follower valve-actuator assembly; during the restoring of the
valve, the pressure of the oil trapped into the oil-chamber
increases disengaging the bucket lifter and the valve from the cam;
for the rest it operates as the first preferred embodiment.
[0032] In a third preferred embodiment, FIG. 12, the bucker lifters
between the push rods and the camshaft are similar to those shown
in the second preferred embodiment. In a Vee engine with a central
cam, or side cam, the long and inevitably flexible linkage from the
cam to the valve reduces the accuracy of the valve motion. Yet the
ECU, based on the feedback from the engine can compensate for the
misalignment between the cylinders, enabling smoother and cleaner
operation. At low revs and loads the engine takes advantage of the
low pumping loss and the over-expansion, while at high revs and
heavy loads the control of the valve duration optimizes the
volumetric efficiency.
[0033] In a fourth preferred embodiment, FIG. 13, the mechanism of
the second preferred embodiment is slightly modified. The
one-way-valve is removed. The release-valve is open during the
opening of the valve, allowing oil to fill the oil-chamber. As long
as the release-valve stays open, the cam controls the restoring of
the valve. When the release-valve finally closes, the valve is
disengaged from the cam and restores under the control of the
release-valve and of the plunger.
[0034] In a fifth preferred embodiment, FIGS. 7 to 11, the
release-valve is an analog valve and needs not to open and close
during every suction cycle. For instance, at 2000 rpm and medium
load the ECU keeps 1/8 open the release-valve, while at 2000 rpm
and full load the ECU keeps 1/4 open the release-valve.
[0035] The release valves can be of any type of the state of the
art, for instance on-off solenoid valves. The loads the
release-valves of this invention undergo and their flow capacity
are smaller in comparison with the loads and the flow capacity of
the release-valves of the closest prior art, i.e. the existing mass
production solenoid on-off valves are more than adequate for the
realization of the present invention.
[0036] Although the invention has been described and illustrated in
detail, the spirit and scope of the present invention are to be
limited only by the terms of the appended claims.
* * * * *