Note: Descriptions are shown in the official language in which they were submitted.
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HYDROELECTRIC DEVICE FOR CLOSED-LOOP DRIVING THE CONTROL
JACK OF A VARIABLE COMPRESSION RATE ENGINE
The subject of the present invention is an electrohydraulic device for closed-
loop control of the control jack of a variable compression ratio engine
comprising at
least one hydraulic transfer valve and one control rack position sensor.
A reference herein to a patent document or other matter which is given as
prior art is not to be taken as an admission that that document or matter was
known
or that the information it contains was part of the common general knowledge
as at
the priority date of any of the claims.
Throughout the description and claims of this specification the word
"comprise" and variations of that word, such as "comprises" and "comprising",
are
not intended to exclude other additives, components, integers or steps.
According to international patents W098/51911, W000/31377 and
W003/008783 belonging to the Applicant, various mechanical devices for a
variable
displacement engine are known.
It is noted that international patent W098/51911 in the name of the Applicant
describes a device used to enhance the overall efficiency of internal
combustion
engines with pistons used at variable load and speed by in-operation
adaptation of
their effective displacement and/or of their volumetric ratio. Since this type
of engine
is known to those skilled in the art by the name "variable compression ratio
engine",
this name will be adopted in the following text.
It is noted that, according to international patent W000/31377 in the name of
the Applicant, the mechanical transmission device for a variable compression
ratio
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engine comprises a piston that is secured in its bottom portion to a
transmission
member interacting on the one hand with a rolling guidance device and, on the
other
hand, with a gearwheel secured to a connecting rod making it possible to
transmit
the movement between said piston and said connecting rod.
It is noted that, according to international patent W003/008783 in the name of
the Applicant, the mechanical transmission device for a variable compression
ratio
engine comprises at least one cylinder in which a piston moves which is
secured, in
its lower portion, to a transmission member interacting on the one hand via a
small-
dimension rack with a rolling guidance device and, on the other hand, by means
of
another large-dimension rack, with a gearwheel secured to a connecting rod.
Said mechanical transmission device for a variable compression ratio engine
also comprises at least one control rack interacting with the gearwheel, means
for
attaching the piston to the transmission member which offer a clamping
prestress,
connection means which make it possible to stiffen the teeth of the racks, and
means for reinforcing and lightening the structure of the gearwheel.
It is observed that according to international patents W098/51911 and
PCT/FR2007/000149, the compression ratio of the variable compression ratio
engine is regulated by means of a control hydraulic jack the movement of which
is
provided by the forces resulting from the inertia of the moving parts and from
the
pressure of the engine gases which are applied to the control rack to which
said jack
is secured. According to these patents, it is noted that the position of the
control jack
always follows that of a control rod which acts on the opening or closing of
valves
which are in contact with the top and bottom faces of the piston of the
control jack.
Said valves allow the hydraulic fluid to pass from the top chamber to the
bottom
chamber of the control jack or vice versa either to decrease or increase the
compression ratio of the variable compression ratio engine. Patents
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PCT/FR2007/000150 and PCT/FR2007/000147 describe a number of variants
making it possible to regulate the position of the control rod by means of one
or more
electric motors controlled by at least one computer.
It is also noted that, according to patent PCT/FR2007/000149, the control jack
comprises a pressurized hydraulic fluid inlet provided to compensate for any
leaks
from said control jack, and to provide a preload pressure for the purpose of
increasing the accuracy of retention of the setpoint in the vertical position
of said
control jack by reducing the effects of the compressibility of the oil while
preventing
any cavitation phenomenon.
As claimed in international patent application PCT/FR2007/000147 in the
name of the Applicant, a single electric motor can control the compression
ratio of
several cylinders via a cam or eccentric shaft. In this same patent, it is
seen that the
regulation of the initial compression ratio of each cylinder may be carried
out by
means of an independent regulation device that can be a threading immobilized
in
rotation.
According to one aspect of the present invention, there is provided an
electrohydraulic device for controlling the compression ratio of a variable
compression ratio engine, comprising:
at least one electrovalve that can open or close at least one hydraulic fluid
duct between a top chamber and a bottom chamber of a control jack;
at least one position sensor of a control rack; and
an angular position sensor of a crankshaft of the engine in order to regulate
the compression ratio and at least one computer,
wherein said top chamber and the bottom chamber of the control jack are
respectively supplied with hydraulic fluid under pressure from a hydraulic
unit via two
booster check valves which open respectively into each of the two chambers and
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which allow the hydraulic fluid to enter said chambers while preventing it
from
leaving.
Other aspects, embodiments, variants and/or resulting advantages of the
present invention, all being preferred and/or optional, are briefly summarized
hereinabove.
For example, the electrohydraulic device for closed-loop control of the
control
jack according to the invention makes it possible to solve a set of problems
associated with controlling the control cylinder(s) of the variable
compression ratio
engine:
- The valves and their springs and the control rod involve providing a
considerable diameter for the control jack, these components being housed in
the periphery of the piston of said jack. This reduces the operating pressure
and the responsiveness of the control jack, increases the transfer flow rates
of
hydraulic fluid between the top chamber and bottom chamber and increases
the space requirement and weight of the control jack assembly.
- The independent control of the compression ratio of each control jack of the
engine is difficult to achieve because, in this case, it is necessary to
provide
an electric actuator for each of the control rods, each actuator being
connected to its control rod by specific transmission means.
- The compression ratio control that is common to all the cylinders of the
variable compression ratio engine involves transmission means between an
electric motor for controlling the compression ratio and the control rods of
each cylinder of the variable compression ratio engine, and regulation means
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specific to each cylinder. These members increase the space requirement,
the weight and the cost price of the variable compression ratio engine.
It would therefore be desirable to reduce significantly the space requirement,
5 the cost price and the weight and to increase the responsiveness and
precision of
the control of the compression ratio of the variable compression ratio engine
that the
device according to the invention makes it possible:
= to delete the control rod and its guidance and sealing means and the
valves
and the springs with which it interacts;
= to reduce the diameter and the displacement of the jack piston for the same
travel for controlling the compression ratio;
= to delete the electric motor for controlling the compression ratio and
the
transmission and regulation means that are associated therewith and that
link it with the control rod.
The electrohydraulic device for controlling the compression ratio of a
variable compression ratio engine according to the present invention comprises
at
least one electrovalve that can open or close at least one hydraulic fluid
duct
between the top chamber and bottom chamber of a control jack, at least one
position
sensor of a control rack, an angular position sensor of the crankshaft of the
engine in
order to regulate the compression ratio and at least one computer, a top
chamber
and a bottom chamber of the control jack that are respectively supplied with
hydraulic fluid under pressure from a hydraulic unit via two booster check
valves
which open respectively into each of the two chambers and which allow the
hydraulic
fluid to enter said chambers while preventing it from leaving.
The electrohydraulic device for controlling the compression ratio of a
variable compression ratio engine according to the present invention comprises
a
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duct between the top chamber and bottom chamber of the control jack which is
arranged in the piston of said jack.
The electrohydraulic device for controlling the compression ratio of a
variable compression ratio engine according to the present invention comprises
a
duct between the top chamber and bottom chamber of the control jack which is
arranged in the cylinder block of the variable compression ratio engine.
The electrohydraulic device for controlling the compression ratio of a
variable compression ratio engine according to the present invention interacts
with a
pinking detector in order to independently regulate the compression ratio of
each
cylinder of the engine according to its own physical characteristics.
The electrohydraulic device for controlling the compression ratio of a
variable compression ratio engine according to the present invention comprises
a
degassing electrovalve making it possible to link the top chamber of the
control jack
with the oil pan of the engine.
The electrohydraulic device for controlling the compression ratio of a
variable compression ratio engine according to the present invention comprises
a
two-way electrovalve comprising no check valve.
The following description with respect to the appended drawings, given as
nonlimiting examples, will make it possible to better understand the
invention, the
features that it has and the advantages that it is capable of providing:
Figure 1 is a schematic view in section illustrating the main components and
their positioning in the variable compression ratio engine of the
electrohydraulic
device according to the invention and according to a first variant embodiment
which
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comprises two independent electrovalves each placed on a circuit furnished
with a
check valve, said electrovalves interacting with a sensor for sensing the
position of
the control rack and a computer.
Figure 2 is a schematic view in section illustrating the main components and
their positioning in the variable compression ratio engine of the
electrohydraulic
device according to the invention and according to a second variant embodiment
which comprises a single electrovalve comprising an electrically-controlled
spool
with two inlets and two separate outlets defining two independent circuits
each
furnished with a check valve, said electrovalve interacting with a sensor for
sensing
the position of the control rack and a computer.
Figure 3 is a schematic view in section illustrating the main components and
their positioning in the variable compression ratio engine of the
electrohydraulic
device according to the invention and according to a third variant embodiment
which
comprises a single electrovalve interacting with a sensor for sensing the
position of
the control rack, a sensor of the angular position of the crankshaft of the
variable
compression ratio engine, and a computer.
DESCRIPTION OF THE INVENTION:
Figures 1 to 3 show an electrohydraulic device 80 for closed-loop control of
the control cylinder 8 of a variable compression ratio engine according to the
present
invention.
According to the patent applications and inventive patents belonging to the
Applicant, the variable compression ratio engine comprises a mechanical
transmission device 1 comprising in the bottom portion of the piston 2 a
transmission
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member 3 secured to said piston and interacting, on the one hand, with a
rolling
guidance device 4, and on the other hand, with a gearwheel 5.
The gearwheel 5 interacts with a connecting rod 6 connected to the
crankshaft 9 in order to transmit the movement between the piston 2 and said
crankshaft 9.
The gearwheel 5 interacts opposite to the transmission member 3 with a
control rack 7 the vertical position of which relative to the cylinder block
100 is
controlled by a control device 12 comprising the control jack 8, the cylinder
piston 13
of which is guided in a jack cylinder 112 arranged in the cylinder block 100.
The control jack 8 comprises, above and below the jack piston 13, a top
chamber 121 and a bottom chamber 122. The control jack 8 consists of a top
jack
rod 10, a bottom jack rod 16 interacting with the jack piston 13.
The top jack rod 10 of the control jack 8 interacts in its extension and in a
sealed manner with a chamber 184 arranged in the cylinder head 300 of the
variable
compression ratio engine.
The top jack rod 10 may comprise in its inner portion and in its center a
booster check valve 185 the inlet of which is in communication with the
chamber 184
arranged in the cylinder head 300 of the control jack 8, while the outlet from
said
booster check valve 185 is connected to a duct 187 arranged in the jack piston
13 of
the control jack 8 and emerging into the bottom chamber 122.
The chamber 184 arranged in the cylinder head 300 is connected via a duct to
another booster check valve 188 housed in said cylinder head and communicating
with the top chamber 121 of the control jack 8.
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Therefore the top chamber 121 and the bottom chamber 122 of the control
jack 8 are respectively supplied with hydraulic fluid under pressure from a
hydraulic
unit via the two booster check valves 185, 188 which open respectively into
each of
the two chambers 121, 122 and which allow the hydraulic fluid to enter said
chambers while preventing them from leaving.
The transmission member 3 secured to the piston 2 is provided on one of its
faces with a first large-dimension rack 35 the teeth 34 of which interact with
those 51
of the gearwheel 5.
The transmission member 3 comprises, opposite to the first rack 35, a second
rack 37 the small-dimension teeth 38 of which interact with those of a roller
40 of the
rolling guidance device 4.
The cylinder block 100 is secured to a support 41 comprising racks 46
synchronizing the movement of the roller 40 of the rolling guidance device 4
with that
of the piston 2.
The electrohydraulic device 80 for controlling the compression ratio of the
variable compression ratio engine comprises at least one electrovalve 81 per
control
jack 8 that can open or close at least one duct 83 of hydraulic fluid between
the top
chamber 122 and bottom chamber 121 of said control jack 8.
The controlling electrohydraulic device 80 comprises, in the cylinder head 300
and at each control jack 8, at least one position sensor 82 making it possible
to
determine, with the aid of at least one computer 84, the position of the
control rack 7.
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The electrohydraulic device 80 for controlling the compression ratio 80 of a
variable compression ratio engine comprises a duct 83 between the top chamber
121 and bottom chamber 122 of the control jack 8 which is arranged in the jack
piston 13 of said control jack 8.
5
As a variant, the duct 83 between the top chamber 121 and bottom chamber
122 of the control jack 8 may be arranged in the cylinder block 100 of the
variable
compression ratio engine.
10
The electrohydraulic device 80 for controlling the compression ratio of a
variable compression ratio engine comprises two electrovalves 81 at an inlet
and an
outlet that can each open or close the duct 83 connecting the top chamber 121
to
the bottom chamber 122 of the control jack 8, as illustrated in figure 1.
Each electrovalve 81 comprises a check valve 85, 86 so that the check valve
85 of the first electrovalve 81 prevents the hydraulic fluid from going from
the top
chamber 121 to the bottom chamber 122 of the control jack 8 but not the
reverse,
while the check valve 86 of the second electrovalve 81 prevents the hydraulic
fluid
from going from the bottom chamber 122 to the top chamber 121 of the control
jack
8 but not the reverse.
Figure 2 illustrates a second variant of the electrohydraulic device 80 for
controlling the compression ratio of a variable compression ratio engine which
comprises an electrovalve 81 comprising two inlets and two outlets which
define two
independent circuits, and a three-position spool 87 making it possible either
to
connect the first inlet to the first outlet, with the second inlet being
closed off, or to
connect the second inlet to the second outlet, with the first inlet being
closed off, or
to close off both inlets.
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In this embodiment, the electrovalve 81 with electrically-controlled spool 87
comprises two check valves 85, 86, the first check valve 85 preventing the
hydraulic
fluid from going from the top chamber 121 to the bottom chamber 121 of the
control
jack 8 but not the reverse, while the second check valve 86 prevents the
hydraulic
fluid from going from the bottom chamber 122 to the top chamber 121 of the
control
jack 8 but not the reverse.
Figure 3 shows a third variant of the electrohydraulic device 80 for
controlling the compression ratio of a variable compression ratio engine which
consists of a single electrovalve 81 that can open or close at least one duct
of
hydraulic fluid 83 between the top chamber 121 and the bottom chamber 122 of a
control jack 8.
In this embodiment, the electrovalve 81 is two-way, comprises no check
valves and can be aperture duty cycle controlled.
In this embodiment, the two-way electrovalve 81 interacts with an angular
position sensor 88 of the crankshaft 9 of the engine in order to regulate the
compression ratio, in addition to the position sensor 82 of the control rack 7
and to
the computer 84.
The two-way electrovalve 81 comprises two parallel channels, one shutoff by
a device with large flow-rate shutoff and slow response, the other shutoff by
a device
for low flow-rate shutoff and fast response.
In each embodiment, the electrohydraulic device 80 for controlling the
compression ratio of the variable compression ratio engine can interact with a
pinking detector, not shown, in order to independently regulate the
compression ratio
of each cylinder 110 of the engine according to its specific physical
characteristics.
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Also, the electrohydraulic device 80 for controlling the compression ratio of
a
variable compression ratio engine comprises a degassing electrovalve, not
shown,
making it possible to connect the top chamber 121 of the control jack 8 with
the oil
pan of the engine.
OPERATION:
According to a particular embodiment, two electrovalves 81 are provided per
control jack 8 at an inlet and an outlet each furnished with a check valve 85,
86 as
illustrated in figure 1, the operation of the electrohydraulic device 80 for
controlling
the compression ratio is as follows:
The forces exerted on the control rack 7 change direction cyclically depending
on the speed and load at which the variable compression ratio engine operates.
Consequently, the pressure of the top chamber 121 of the control jack 8
becomes cyclically higher and cyclically lower than that of the bottom chamber
122
of the control jack 8.
When, in order to optimize the efficiency, the torque or reduce the polluting
emissions of the variable compression ratio engine, it is necessary to reduce
the
compression ratio, the opening of the electrovalve 81 for reducing the
compression
ratio is commanded by the computer 84.
Taking account of the forces applied to the control rack 7, and of the ratchet
effect produced by the check valve 86 placed on the same duct 83 as the
electrovalve 81 that is kept open, said control rack 7 moves in one or more
stages
until the position sensor 82 of said control rack 7 indicates to the computer
84 that
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the position of said control rack 7 correctly corresponds to the required
compression
ratio.
The operation is identical when it involves raising the compression ratio of
the
engine, but then involves the opening of the other electrovalve 81 for
increasing the
compression ratio, interacting with the check valve 85.
If there is a leakage of hydraulic fluid between the top chamber 121 and the
bottom chamber 122 of the control jack, the position sensor 82 of the control
rack 7
informs the computer 84 of the progressive drift in the position of the
control rack 7.
Beyond a certain difference between the setpoint position and the real
position of the control rack 7, the computer 84 opens either the electrovalve
81 for
reducing the compression ratio or the electrovalve 81 for increasing the
compression
ratio in order to reestablish the setpoint position of said control rack 7.
If a leakage of hydraulic fluid occurs between either one of the top chamber
121 or bottom chamber 122 of the control jack 8 and the outside of said jack,
said
leakage is automatically compensated for by provision of hydraulic fluid into
the
chamber opposite to the chamber that leaks, said fluid originating from a
hydraulic
unit as described, for example, in patent application FR 06/00714 belonging to
the
Applicant and being provided via one or other of the booster check valves 185,
188.
The second variant embodiment set out in figure 2 operates according to the
same principle as that previously described in figure 1, except that the
functions of
the distinct electrovalves 81 are in this case performed by a single
electrovalve 81
comprising an electrically-controlled spool 87 with two inlets and two
outlets.
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It is however different from the embodiment set out in figure 3, which
provides
for the deletion of the check valves 85, 86 to the benefit of an angular
position
sensor 88 of the crankshaft 9 of the variable compression ratio engine, it
being
understood that this member already exists in most modern engines.
According to the particular embodiment set out in figure 3, a single two-way
electrovalve 81 is provided, said electrovalve being capable of opening and
closing
sufficiently rapidly to allow the movement of the control rack 7 only for a
few degrees
of angular movement of the crankshaft 9.
According to the embodiment set out in figure 3, the computer 84 incorporates
in its memory the ranges of angular position of the crankshaft 9 during which
the
force applied to the control rack 7 goes in the direction of increasing or
reducing the
compression ratio when the duct which connects the top chamber 121 and the
bottom chamber 122 of the control jack 8 is open.
According to this embodiment, the mapping of the direction of the force
applied to the control rack 7 that the computer 84 contains covers the whole
range of
operating speed and load of the variable compression ratio engine.
When, in order to optimize the efficiency, the torque or reduce the polluting
emissions of the variable compression ratio engine, it is necessary to reduce
the
compression ratio of said engine, the computer 84 commands the opening of the
two-way electrovalve 81 only when the angular position of the crankshaft 9
coincides
with a force applied to the control rack 7 which goes in the direction of
reducing the
compression ratio.
Conversely, to increase the compression ratio of the variable compression
ratio engine, the computer 84 commands the opening of the two-way electrovalve
81
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only when the angular position of the crankshaft 9 coincides with a force
applied to
the control rack 7 which goes in the direction of increasing the compression
ratio.
These two operations occur and are repeated as long as necessary and until
5 the control rack 7 is moved in one or more stages until the position
sensor 88 of said
control rack 7 indicates to the computer 84 that the position of said rack
correctly
corresponds to the required compression ratio.
The scope of the claims should not be limited by the preferred embodiments
10 set forth in the examples, but should be given the broadest
interpretation consistent
with the description as a whole.
