U.S. patent application number 15/748293 was filed with the patent office on 2018-08-02 for device for separation of oil, ventilation system, cylinder head cover and internal combustion engine.
The applicant listed for this patent is REINZ-DICHTUNGS-GMBH. Invention is credited to SEBASTIAN BRINKER, YAGIZ YAMAN, PHILIPP ZEDELMAIR, FRANCESCO ZITAROSA.
Application Number | 20180216509 15/748293 |
Document ID | / |
Family ID | 53765192 |
Filed Date | 2018-08-02 |
United States Patent
Application |
20180216509 |
Kind Code |
A1 |
BRINKER; SEBASTIAN ; et
al. |
August 2, 2018 |
DEVICE FOR SEPARATION OF OIL, VENTILATION SYSTEM, CYLINDER HEAD
COVER AND INTERNAL COMBUSTION ENGINE
Abstract
A device for separation of oil droplets and/or oil mist from
blow-by gases of an internal combustion engine. Also described is a
ventilation system for ventilation of the crankcase of an internal
combustion engine, a cylinder head cover and an internal combustion
engine, which contain such a device.
Inventors: |
BRINKER; SEBASTIAN;
(NEU-ULM, DE) ; YAMAN; YAGIZ; (NEU-ULM, DE)
; ZEDELMAIR; PHILIPP; (ULM, DE) ; ZITAROSA;
FRANCESCO; (ILLERTISSEN, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
REINZ-DICHTUNGS-GMBH |
NEU-ULM |
|
DE |
|
|
Family ID: |
53765192 |
Appl. No.: |
15/748293 |
Filed: |
March 16, 2016 |
PCT Filed: |
March 16, 2016 |
PCT NO: |
PCT/EP2016/055675 |
371 Date: |
January 29, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 45/08 20130101;
F01M 13/00 20130101; B01D 45/06 20130101; F01M 13/04 20130101; F16K
15/16 20130101; F01M 2013/0044 20130101; B01D 45/16 20130101; F01M
2013/0433 20130101 |
International
Class: |
F01M 13/04 20060101
F01M013/04; B01D 45/08 20060101 B01D045/08; B01D 45/06 20060101
B01D045/06; F16K 15/16 20060101 F16K015/16 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2015 |
DE |
20 2015 103 977.8 |
Claims
1-16. (canceled)
17. A device for separation of oil droplets and/or oil mist from
blow-by gases of an internal combustion engine, having a valve for
control of the gas flow from a pressure side to a suction side of
the device, the valve having at least one base plate, comprising:
at least one first region of the at least one base plate, there
being disposed in each of the first regions at least one first gas
passage opening for passage of gas from the pressure side to the
suction side of the base plate and also, on the pressure side of
the at least one base plate, and at least one first valve closure
for pressure-side closure of the at least one first gas passage
opening.
18. The device according to claim 17, wherein the first valve
closure of each of the first regions has a pretension such that it
closes the first gas passage openings overlapped by it when the low
pressure of the suction side relative to the pressure side exceeds
a predetermined low pressure in magnitude.
19. The device according to claim 17, wherein at least two first
regions of the at least one base plate, wherein the predetermined
threshold values of the valve closure of at least two of the at
least two first regions are different from each other.
20. The device according to claim 17, further comprising a second
region of the at least one base plate, which is disposed adjacent
to the side of the first region, and in which at least one second
unclosable gas passage opening for passage of gas from the pressure
side to the suction side of the valve is disposed.
21. The device according to claim 17, wherein at least one of the
first valve closure has a first resilient tongue which is disposed
on the pressure side of the base plate.
22. The device according to claim 21, wherein at least one of the
first resilient tongues is attached resiliently to the base plate
via at least one retaining arm such that it is movable between a
first position, in which it uncovers the first gas passage openings
overlapped by it, and a second position, in which it closes the
first gas passage openings overlapped by it.
23. The device according to claim 22, wherein the retaining arm
has, between its attachment to the base plate and the region of the
resilient tongue overlapping the gas passage opening, at least two
bends which are opposite each other.
24. The device according to claim 21, wherein at least one of the
first resilient tongues is configured such that at least one of the
first gas passage openings overlapped by it is unclosable by the
first resilient tongue.
25. The device according to claim 21, wherein at least one of the
first gas passage openings on the pressure side of the base plate
has an edge which protrudes in a web-shape from the base plate and
extends circumferentially about the first gas passage opening as
support for the first resilient tongue covering the first gas
passage opening.
26. The device according to claim 25, wherein the circumferential
edge is circumferentially the same height or is flattened in the
direction of the mounting of the first resilient tongue or has an
additional sealing element which extends circumferentially on the
edge.
27. The device according to claim 21, wherein at least one of the
first resilient tongues has an embossing which extends
circumferentially about at least one of the first gas passage
openings.
28. The device according to claim 27, wherein the at least one
embossing is a bead-shaped embossing or a circumferential sealing
element.
29. The device according to claim 17, wherein at least one of the
at least one first gas passage openings has a narrowed
cross-section which acts as oil separator element.
30. The device according to claim 17, wherein in at least one of
the at least one first gas passage openings, there is disposed a
flow-deflection- and -guiding element as oil separator element, in
particular a helix-shaped element.
31. The device according to claim 30, wherein the oil separator
element is a helix-shaped element.
32. A ventilation system for ventilation of the crankcase of an
internal combustion engine comprising: an intake duct with a
compressor and a throttle valve, having an oil separator with a gas
input chamber and at least two separate gas output chambers
connected thereto, a first ventilation pipe for connecting the
crankcase of the internal combustion engine and the gas input
chamber of the oil separator, a first output pipe for connecting
the first gas output chamber to the intake duct of the internal
combustion engine before the compressor, and a second output pipe
for connecting the second output chamber to the intake duct of the
internal combustion engine behind the throttle valve, wherein in
the second gas output chamber, there is disposed a device for
separation of oil droplets and/or oil mist.
Description
[0001] The present invention relates to a device for separation of
oil droplets and/or oil mist from blow-by gases of an internal
combustion engine. Furthermore, it relates to a ventilation system
for ventilation of the crankcase of an internal combustion engine,
a cylinder head cover and an internal combustion engine, which
include such a device.
[0002] In the crankcase of an internal combustion engine, blow-by
gases occur, which are guided normally, in particular for
environmental reasons, into the intake duct of the internal
combustion engine. It must thereby be ensured that the pressure
applied in the crankcase is maintained within the narrow required
upper and lower limiting values. For this purpose, the blow-by
gases are discharged out of the crankcase via a ventilation pipe,
for which purpose the pressure difference between the crankcase and
the intake duct of the internal combustion engine is used.
[0003] A ventilation system for a crankcase for transporting
blow-by gases therefore normally has a ventilation pipe from the
crankcase to the intake duct of an internal combustion engine. In
the ventilation pipe, generally an oil separator/oil mist separator
is disposed furthermore in order to separate oil and oil mist,
which are contained in the blow-by gases, from the blow-by gases.
For this separation, likewise the pressure difference between the
crankcase and the intake duct is used. This means that the pressure
difference between the intake duct and the crankcase is used
suitably for throughflow of an oil separator/oil mist separator and
therefore is likewise subject to certain limits. In particular, the
ventilation must be controlled such that, on the one hand, the
occurring blow-by gas flows are discharged safely and, on the other
hand, the pressure decrease over the oil separator is within an
optimum range for efficiency of the oil separation.
[0004] In particular in the case of internal combustion engines
with supercharger device/compressor, for example a turbocharger or
a compressor, and also a throttle valve, different pressure ratios
which depend upon the operating state of the internal combustion
engine occur in different sections of the intake pipe between the
air filter and the inlet valve of the engine for fresh air.
[0005] In full load operation, a very high pressure which cannot be
used for suctioning-out and ventilation of the crankcase occurs in
the intake pipe behind the supercharger device. Only the low
pressure which is applied in the intake pipe between the air filter
and the supercharger device can be used for this purpose in full
load operation.
[0006] In partial load operation or even in coasting operation, an
intense low pressure, which can be used advantageously for
ventilation of the crankcase, exists in the region between the
throttle valve and the inlet valve of the internal combustion
engine.
[0007] Here, as in the following, there is considered as full load
operation of the internal combustion engine, an operation with
extensively or completely opened throttle valve and/or an operation
with a pressure of 0 to 700 mbar, advantageously of 0 to 400 mbar,
in the ventilation pipe connected to the intake pipe behind the
throttle valve and/or with a pressure of 0 to -200 mbar,
advantageously of 0 to -60 mbar, in the ventilation pipe connected
to the intake pipe in front of the supercharger device. As partial
load operation or no-load operation or coasting operation, there is
denoted, here as in the following, a load operation with
extensively (partial load operation) or completely (coasting
operation) closed throttle valve or an operation at a pressure of 0
to -900 mbar, advantageously of 0 to -750 mbar, in the ventilation
pipe connected to the intake pipe behind the throttle valve, and/or
an operation with a pressure of 0 to -150 mbar, advantageously of 0
to -60 mbar, in the ventilation pipe connected to the intake pipe
in front of the supercharger device. The pressures should be
understood respectively relative to the atmospheric external
pressure.
[0008] It is therefore normal to split the ventilation pipe from
the crankcase to the intake duct into two pipes, one of which opens
into the intake duct between the air filter and the supercharger
device and the other of which opens into the intake pipe behind the
throttle valve between throttle valve and inlet valve of the
internal combustion engine. With suitable interconnection of the
ventilation pipe, now, on the basis of the low pressure present in
different sections of the ventilation pipe in different operating
states, the crankcase can be reliably ventilated.
[0009] The ventilation pipe between the crankcase and the intake
duct normally has, in the common part of the ventilation pipe, an
oil coarse separator with which oil droplets and oil mist can be
separated roughly. In the ventilation partial pipes which connect
the common part of the ventilation pipe to the intake pipe in front
of or behind the compressor, further oil separators/oil mist
separators which contribute to a further improved oil separation
can be introduced.
[0010] In partial load- or coasting operation, i.e. in the case of
a partially or completely closed throttle valve, a very low
pressure is present in the intake duct behind the supercharger
device and hence a very high pressure gradient (high pressure
difference) between the crankcase and the intake duct. In addition,
the blow-by gas comprises, in particular in coasting operation, a
considerable proportion of unconsumed fuel. Therefore in partial
load- or coasting operation, normally a fresh air supply is made
possible from the intake duct, typically from the intake pipe in
front of the supercharger device, counter to the ventilation
direction through the full load ventilation pipe so that the low
pressure produced in the crankcase is limited and the blow-by gases
are diluted so that the proportion of toxic substances in the
exhaust gases is reduced.
[0011] In partial load operation, an acceptable mixture of blow-by
gases and fresh air is present. However, if the engine switches
over into coasting operation, a very high content of uncombusted
hydrocarbon compounds occurs suddenly in the blow-by gases which,
in the case of immediate further conveyance through the intake duct
and engine to the catalyst, would lead to overheating and hence
destruction of the catalyst because of combustion of the
hydrocarbon compounds. In order to avoid this, it is essential that
only specific, namely limited quantities of uncombusted hydrocarbon
compounds are conveyed further to the catalyst. In order to counter
this, it would be conceivable to dilute the HC-rich exhaust gas
greatly via a very high volume flow of fresh air, however in order
to stop impermissible pressures occurring here, it would however
also be necessary to have an accelerated discharge of this mixture,
which would then again lead to a supply of a large quantity of
uncombusted hydrocarbons to the catalyst. Hence it is necessary to
limit the supply of HC-rich blow-by gases to the engine or catalyst
in coasting operation via other measures.
[0012] For this purpose, inter alia, in the ventilation partial
pipe provided for the partial load- or coasting operation between
the oil separator and the intake duct, there can be disposed,
between the supercharger device and the inlet valve, a valve which
is controlled, in particular electrically, by the engine or valve
train of the engine, which valve has a high pressure decrease in
coasting operation and hence restricts both the volume flow of
throughflowing gases and prevents a breakdown of the intense low
pressure in the intake duct towards the crankcase. This and other
conventional solutions however generally require a large number of
parts and are therefore complex, cost-intensive and
assembly-intensive.
[0013] It is therefore the object of the present invention to make
available a device for separation of oil droplets and/or oil mist
from blow-by gases of an internal combustion engine, and also
ventilation systems, cylinder head covers and internal combustion
engines including these, which require few individual parts, are
easy and economical to produce and assemble and enable a compact
construction. In particular, the device according to the invention
for separation of oil droplets and/or oil mist is intended to make
it possible to control suitably the volume flow of gases in the
ventilation pipe to the intake duct of the engine in partial load
operation and in coasting operation.
[0014] This object is achieved by the device for separation of oil
droplets and/or oil mist from blow-by gases of an internal
combustion engine according to claim 1. Furthermore, this object is
achieved by the ventilation system according to claim 14, the
cylinder head cover according to claim 15 and the internal
combustion engine according to claim 16. Advantageous developments
of the present invention are given in the dependent claims.
[0015] The device according to the invention for separation of oil
droplets and/or oil mist from blow-by gases of an internal
combustion engine is inserted as oil separator/oil mist separator,
in particular in the ventilation pipe, in particular in the partial
ventilation pipe, which opens into the intake pipe behind the
supercharger device. It has a valve for control of the gas flow
from a pressure side to a suction side of the device.
[0016] With an arrangement of this device in a ventilation pipe
from a crankcase to an intake pipe of an intake duct of an internal
combustion engine, the side orientated towards the crankcase is
thereby subsequently termed pressure side and the side orientated
towards the intake pipe, suction side, even if, under a few,
specific operating conditions of the internal combustion engine,
the actual pressure ratios can turn out to be different.
[0017] This valve, which has also an oil separation function at the
same time, has at least one base plate. The base plate can be
configured in one piece or consist of partial plates which are
disposed adjacently to each other and successively perpendicular to
the plate plane. This base plate has one or more first regions, at
least one first gas passage opening for passage of gas from the
pressure side to the suction side of the base plate being present
in each of the first regions, if present. The present valve is
characterised in particular in that, for one or a plurality or all
of these first regions, respectively one first valve closure is
provided, which can close the first gas passage openings situated
in the respective region.
[0018] This valve closure is disposed or attached, according to the
invention, on the pressure side on the base plate. By means of the
pressure-side arrangement of the valve closure, it is possible to
control the gas passage through one of the first regions such that
the respective valve closure closes the associated first gas
passage opening covered by it (or if present, the plurality of gas
passage openings present in the respective region), if the low
pressure on the suction side relative to the pressure side exceeds
a specific limiting value. This leads to the fact that, during
transition of the operating state of the engine from full load-,
via partial load-, to coasting operation, which is associated with
increasing low pressure on the suction side of the device according
to the invention, the passage cross-section for the gases to be
ventilated from the crankcase into the intake duct is reduced.
Hence the pressure decrease is increased increasingly over the
device according to the invention during transition from full
load-, via partial load-, to coasting operation of the engine so
that the crankcase is protected from too low a low pressure and the
volume flow is increasingly limited via the device according to the
invention. At the same time, a controlled and in particular limited
supply of hydrocarbon-rich blow-by gas is made possible to the
intake duct or to the catalyst, as a result of which the entry of
hydrocarbons into the catalyst is limited, the exhaust gas
temperatures are kept within a permissible range and damage to a
catalyst can be avoided.
[0019] In particular, the device according to the invention can
have at least two or more first regions, the valve closures of both
or a plurality of first regions having different opening/closing
characteristics. As a result of the fact that the valve closures of
the individual regions in the device according to the invention
close at different pressure differences between the suction side
and the pressure side of the device according to the invention, the
valve closure close in succession during transition from full
load-, via partial load-, to coasting operation. This leads to a
successive increase in the pressure decrease over the device
according to the invention and a successive reduction in the free
passage cross-section of the device according to the invention and
hence of the volume flow of blow-by gases flowing over the device.
Advantageously, the base plate of the device according to the
invention can be provided in addition with a gas passage opening
which is unclosable. Alternatively, also at least one of the valve
flaps can be provided with an opening which is situated, in flow
direction, downstream of one of the gas passage openings covered by
it so that the respective gas passage opening is not closed
completely even during closure of the valve flap. These gas passage
openings of the valve, which are in no case completely closable,
ensure a minimum passage of blow-by gases, even in coasting
operation at maximum suction-side low pressure. The cross-section
of these unclosable openings determines the overall volume flow
over the device according to the invention in coasting operation of
the engine.
[0020] Advantageously, the at least one base plate can be a
one-piece component which is produced, for example, in injection
moulding technology. As a result, as further components of the
device according to the invention, only respectively one further
component for the first valve flaps alone, for example designed as
resilient tongue, for example this elastic tongue itself, is
required. The entire device according to the invention for
separation of oil droplets and/or oil mist has therefore very few
parts and can therefore be produced and also assembled economically
and compactly.
[0021] The optional, first resilient tongues according to the
invention can respectively have a retaining arm which is mounted
resiliently on the valve body, here the base plate, such that the
resilient tongue is movable between a first position, in which it
closes the first gas passage openings covered by it, and a second
position, in which it uncovers the first gas passage openings
covered by it.
[0022] Each of the resilient tongues can--as already described
above--be pretensioned such that, above a predetermined low
pressure between the suction side and the pressure side, it closes
the respective covered first gas passage openings and opens them
above a predetermined positive pressure difference. The pretension
can thereby be chosen differently for each resilient tongue.
[0023] The retaining arm or the retaining arms can advantageously
be configured, according to the invention, such that two different
pretensions must be overcome for closing the gas passage openings
in succession.
[0024] For example, the first pretension can have the effect that,
with the initial low but increasing low pressure, the resilient
tongue is moved towards the gas passage openings to be closed by
this resilient tongue until the resilient tongue abuts against a
limit stop region, preferably against a web-like wall of a gas
passage opening, without however closing the latter completely. As
a result, the gap between the gas passage openings to be closed and
the resilient tongue is reduced and thus the pressure decrease over
the valve is increased and also the volume flow is reduced.
[0025] For this purpose, for example the retaining arm can have a
first joint-like bend which is provided between the attachment
point of the retaining arm to the valve body and the region of the
resilient tongue covering the gas passage openings. Starting from
the attachment point, the first bend is produced leading away from
the valve body.
[0026] A second joint-like bend in the opposite direction to the
first bend can be provided between the first bend and the region of
the resilient tongue covering the passage openings.
[0027] If now the suction-side low pressure increases, then the
resilient tongue is deflected firstly, as described above, at the
first bend until it abuts against a limit stop element, for example
a wall of a gas passage opening.
[0028] If the suction-side low pressure is further increased, the
resilient tongue is suctioned further in the direction of the gas
passage openings around this limit stop element and thereby
describes a rotation in the second bend, preferably on or in the
vicinity of the limit stop element, so that the resilient tongue
closes the gas passage openings.
[0029] As a result of the first pretension in the first bend, the
resilient tongue is therefore pretensioned at a low intake low
pressure by the long lever of the retaining arm up to the mentioned
limit stop element. By means of the limit stop, the lever length of
the retaining arm is then shortened. For ultimate covering and
closing of the gas passage openings, a greater force must then be
applied, i.e. an even higher low pressure must be applied. The
opening of the gas passage openings is effected with a lower
pressure hysteresis relative to the closing pressure required for
closing the gas passage openings. As a result, the resilient tongue
is thus prevented from uncovering again the gas passage openings
only with a very low suction-side low pressure. This enables rapid
transition from coasting- to partial load operation.
[0030] Furthermore, it is possible to configure the first resilient
tongue such that it uncovers the first gas passage openings covered
by it in succession during opening. As a result of the successive
uncovering of the first gas passage openings, the pressure decrease
over the base plate, which is determined by the total cross-section
of all respectively uncovered first gas passage openings, is
controlled gradually or quasi-continuously.
[0031] The first gas passage openings can have, on the side
orientated respectively towards the first valve closure, a
web-shaped edge which protrudes in a wedge-shape from the base
plate and extends circumferentially about the respective gas
passage opening as support for the first valve closure. This
web-shaped circumferential edge can thereby protrude overall at the
same distance circumferentially from the base plate, i.e. be the
same height.
[0032] Alternatively, the edge can also be flattened in the
direction of the mounting of the valve closure so that the valve
closure comes to lie on the bevelled edge with pretension.
[0033] The protruding edge is in principle suitable as support for
the respective valve closure and, in addition, forms a seal between
the gas passage opening and the valve closure. Alternatively, also
a circumferential embossing, in particular a bead-shaped embossing,
can be inserted in the respective valve closure (for example if the
latter is manufactured from a metal sheet), in particular in the
respective resilient tongues, in order to form a better seal of the
respective gas passage opening by the associated valve closure. As
circumferential sealing elements, also coatings both of the base
plate and of the valve closure are possible. The coatings can
thereby be configured partially or also over the entire surface.
The valve closure can also be manufactured from a precoated metal
sheet.
[0034] The first gas passage openings in the first region of the
base plate have, in addition to their function of controlling the
volume flow of the gas throughflow, in particular also the object
of separating oil droplets and/or oil mist from the blow-by gases
passing through. This is effected, on the one hand, even in the
case of gas passage openings which do not have a further special
configuration, since there, because of the narrowing relative to
the chamber in front of the gas passage openings, the gas flow is
accelerated, or is slowed down at the outlet of the gas passage
openings because of the widening. This leads to a separation of oil
droplets and/or oil mist situated in the blow-by gas flow. In order
to improve the separation performance further, the cross-section of
one, of a plurality of or of all of the gas passage openings can
also have a nozzle-shaped design.
[0035] In a further embodiment of the invention, at least two of
the first gas passage openings, preferably two first gas passage
openings covered by different resilient tongues, can have different
cross-sections of their inlets and/or of their outlets and/or
centrally between their inlets and their outlets, in particular
with respect to the cross-sectional area and/or cross-sectional
shape.
[0036] Furthermore, it is possible, in order to improve the
separation performance, to dispose, in one, a plurality of or all
the first gas passage openings in the base plate, a guiding
geometry. This guiding geometry can serve in particular for setting
the blow-by gases passing through in a rotational movement about
the axial direction/throughflow direction of the respective gas
passage opening.
[0037] For this purpose, in at least one of the gas passage
openings, a for example helical guiding geometry can be disposed,
which sets the throughflowing gases in rotation about the axial
direction of the gas passage opening. If the valve body has a
plurality of partial base plates, then, on the one hand, guiding
geometries can be disposed, in the first gas passage openings, only
in one of the partial base plates. On the other hand however,
guiding geometries can be disposed, also in gas passage openings,
disposed successively in flow direction, in partial base plates
disposed adjacently to each other, guiding geometries disposed
successively in gas flow direction having the same, however
preferably opposite, direction of rotation. The guiding geometries
can thereby change in their throughflow direction, for example
widen. The guiding geometries can be designed, in particular as
presented in DE 10 2004 037 157 A1 or in DE 20 2014 002 795 U1. The
disclosure content of DE 10 2004 037 157 A1 and of DE 20 2014 002
795 U1 is herewith integrated entirely in the present application,
in particular with respect to the configuration and arrangement of
the guiding geometries described therein.
[0038] In the case of the device according to the invention, in
total two or more resilient tongues can be provided in the first
region. In the case of two or more resilient tongues, these can
have a common attachment region for attachment of the resilient
tongues to the base plate. By means of a common attachment region,
the attachment region can have a smaller design, material can be
saved, space can be made available on the base plate for other
components of the valve and/or the valve can have an overall
smaller design.
Advantageously, at least two or more resilient tongues can be
produced as a one-part element, for example as sheet metal stamped
part, in particular from spring-hardened steel. This makes
possible, in addition to simpler manufacture, also easier handling
and easier assembly, since only one element is present instead of a
plurality of individual parts.
[0039] In a further advantageous embodiment of the invention, at
least one of the resilient tongues is attached resiliently to the
base plate via at least one retaining arm such that it is movable
between a first position, in which it closes the covered gas
passage openings, and a second position, in which it uncovers the
covered gas passage openings. As a result, the pressure difference
between the suction- and the pressure side of the valve can be
adjusted continuously.
[0040] At least one of the retaining arms can be attached such that
the resilient tongue attached via the retaining arm is movable such
that it is removed successively from the gas passage openings
covered by it or closes these successively. As a result, the
pressure difference and the volume flow between the suction- and
the pressure side of the valve can be adjusted more precisely and
continuously. As a result, the oil separator can be operated as a
function of the volume flow at an operating point with an optimum
number of opened/uncovered passage openings.
[0041] At least one of the retaining arms can also be attached such
that the associated resilient tongue is removed in a tilting
movement from at least two gas passage openings or is moved towards
these. Also as a result, a predetermined pressure decrease between
a suction- and a pressure side of the valve can be adjusted more
precisely.
[0042] A further advantageous embodiment of the invention provides
that two retaining arms are provided for each of the first
resilient tongues, which retaining arms extend along two opposite
edges of the resilient tongue and enclose between themselves one of
the resilient tongues in the positional plane of the resilient
tongue, the retaining arms being attached at one of their ends
(directly or indirectly) to the base plate and being connected, at
their other end, to the resilient tongue, possibly in one piece. In
the case of this attachment, the resilient tongue can be removed
from the gas passage openings in parallel in the case of a
sufficiently high pressure difference and hence all of the covered
gas passage openings open at the same time and to the same degree.
In other words, when opening the gas passage openings, the spacing
between the resilient tongue and the gas passage openings remains
essentially constant over the surface area of the resilient tongue.
In order that the first resilient tongue is removed evenly from the
covered first gas passage openings in this manner, two bending
regions or three bending points can be provided. One bending region
is situated advantageously in the region of the attachment of the
retaining arms to the base plate, i.e. respectively one bending
point on each retaining arm. A second bending region is situated
advantageously in the region of the one-piece connection between
the retaining arms and the resilient tongue. The bending regions
extend essentially parallel to each other and possibly parallel to
a straight line which connects attachment points of the retaining
arms on the base plate to each other.
[0043] Preferably, the retaining arms, viewed in radial direction,
i.e. directed away from the attachment points of the retaining arms
on the base plate, are connected to the resilient tongue behind the
last gas passage opening which can be closed by the resilient
tongue, possibly in one piece.
[0044] At least one of the first resilient tongues can also be
attached pretensioned such that it only opens the covered first gas
passage openings when the pressure difference between the pressure
side and the suction side is above a predetermined threshold value.
For this purpose, the resilient tongues or the retaining arms
thereof or attachment regions are deformed specifically, preferably
in portions, before or during use. For this purpose, preferably the
support faces of the resilient tongues or of the attachment regions
on the surface of the base plate are bent.
[0045] The device according to the invention can have furthermore,
in an advantageous embodiment, an additional non-return valve in
the outlet pipe of the partial load train subsequent to the gas
output chamber which, in the case of high pressure in the section
of the intake pipe behind the throttle valve, as can happen for
example in full load operation, prevents a return flow of fresh air
from this section of the intake pipe to the gas output chamber.
[0046] The valves or valve closures of devices according to the
invention concern passive elements which in fact can possibly be
pretensioned but are controlled individually by the pressure
ratios. They manage therefore without additional actuators or
electrical or magnetic control units or the like.
[0047] In the following, some examples of devices according to the
invention, ventilation systems according to the invention, cylinder
head covers according to the invention and internal combustion
engines according to the invention are now given. The same or
similar elements are thereby provided with the same or similar
reference numbers and therefore the description thereof is possibly
not repeated. In the case of the following examples, each of the
examples comprises a large number of additional optional,
advantageous developments of the present invention. These can
respectively also develop the present invention individually and
not only in the illustrated combination. In particular, it is also
possible to use combinations of such optional advantageous
developments from different subsequent examples together for
advantageous development of the present invention, without likewise
taking into account respectively all further optional, advantageous
developments of the present invention according to the respective
examples.
[0048] There are shown
[0049] FIG. 1 an internal combustion engine according to the
invention;
[0050] FIG. 2 a device according to the invention as can be used in
a valve cover according to the invention or in the internal
combustion engine according to the invention according to FIG.
1;
[0051] FIGS. 3 to 8 respectively a further example of a device
according to the invention.
[0052] FIG. 1 shows an internal combustion engine as combustion
vehicle in schematic cross-section. The internal combustion engine
1 has a crankcase 2, a cylinder head 3 and also a cylinder head
cover/valve cover 4. Furthermore, the internal combustion engine 1
has an intake duct 10 with an air filter 11, an intake pipe 12 with
pipe sections 12a, 12b and 12c, a supercharger device 13, for
example a turbocharger or a compressor, and also a throttle valve
14. The intake pipe 12 leads, with its section 12a, from the air
filter 11 to the supercharger device 13, with its section 12b, from
the supercharger device 13 to the throttle valve 14 and, with its
section 12c, from the throttle valve 14 to an intake manifold 5 on
the cylinder head 3.
[0053] In FIG. 1, a ventilation pipe 22 which connects the
crankcase 2 to an oil separator 20 is illustrated. In the part of
the ventilation pipe 22 opening into the oil separator 20, a coarse
oil separator 24 can be disposed. Also in other regions of the
ventilation pipe, a coarse oil separator can be provided.
[0054] The oil separator 20 has a gas input chamber 21 into which
the ventilation pipe 22 opens. The ventilation pipe 22 is
illustrated in FIG. 1 as integral element, however it can also lead
externally from the crankcase to the oil separator 20.
[0055] The gas input chamber 21 serves as settling chamber and
forms a pre-chamber in the oil separator 20.
[0056] The oil separator 20 has, furthermore, a gas output chamber
25, subsequently termed gas output chamber 25 in full load train,
and also a gas output chamber 26, subsequently termed gas output
chamber 26 in partial load train. Both gas output chambers 25 and
26 are connected to the gas input chamber 21 so that the blow-by
gases can flow from the ventilation pipe 22 via the gas input
chamber 21 into the gas output chambers 25 and 26.
[0057] Between the gas input chamber 21 and the gas output chambers
25 and 26 or at the beginning of the gas output chambers 25 and 26,
devices respectively for separation of oil droplets and oil mist
are disposed. These devices are flowed through by the blow-by
gases, starting from the gas input chamber 21, in full load-, or
partial load-, and coasting operation, oil droplets and oil mist
being separated from the throughflowing blow-by gases.
[0058] The gas output chamber 25 in full load train is connected
via a first output pipe 15 to the section 12a of the intake pipe
12. It is also possible to design the gas output chamber 25 itself
as part of this first output pipe 15. The gas output chamber 26 is
connected via a second output pipe 16 to the section 12c of the
intake pipe 12. Here also, the gas output chamber 26 can also be
designed as part of the second output pipe 16.
[0059] The invention now relates essentially to the device 28 for
separation of oil droplets/oil mist which is disposed in FIG. 1 in
the output chamber 26 as device according to the invention for
separation of oil droplets and/or oil mist from blow-by gases.
[0060] The device according to the invention has a valve 30 for
control of the gas flow from the pressure side to the suction side
of the device in partial load train. The pressure side, in partial
load train, is the side orientated toward the crankcase 2, whilst
the suction side is the side orientated towards the intake duct 10.
The valve 30 according to the invention has a base plate 35 which
comprises, in at least one first region, first gas passage openings
for passage of gas from the pressure side to the suction side. As
is explained later, the device according to the invention in FIG.
1A has two such first regions which respectively comprise separate
first gas passage openings. For groups of gas passage openings,
respectively one valve flap is disposed on the pressure side on the
respective base plate. Each of these valve flaps is pretensioned
such that it closes, with sufficient low pressure in the gas output
chamber 26, one, a plurality or all of the gas passage openings
covered by it.
[0061] In the pipe 16, a non-return valve 6 is disposed subsequent
to the gas output chamber 26, which valve, in the case of high
pressure in section 12c of the intake pipe 12, as can occur for
example in full load operation, prevents return flow of fresh air
from section 12c to the gas output chamber 26.
[0062] In FIG. 1A, the internal combustion engine is now
illustrated in partial load operation state with an opened
non-return valve 6. In the latter, the valve flap is opened in one
of the first regions in the device according to the invention and,
in another region, the valve flap is closed. As a result, only the
gas passage openings in the first-mentioned region are available
for passage of the blow-by gases.
[0063] In FIG. 1B, the same internal combustion engine is
illustrated in coasting operation. In coasting operation, the valve
flaps are in a closed state in both regions so that the associated
gas passage openings are no longer available for further conveyance
of the blow-by gases and the fresh air supplied for scouring. As is
explained later, a further, second gas passage opening, which is
unclosable, is situated however for example in the base plate. This
is sufficient to ensure adequate ventilation of the crankcase in
coasting operation since the non-return valve 6 is opened at the
same time. On the basis of the small cross-sectional area thereof,
it produces a very high pressure decrease so that the crankcase is
protected from the very high low pressure in the partial pipe 12c
of the ventilation pipe 12 and, at the same time, the volume flow
of throughflowing gases, in particular the volume flow of blow-by
gases, with a high proportion of uncombusted hydrocarbons, is
limited.
[0064] FIG. 1C shows the same internal combustion engine in full
load operation. In full load operation, a high pressure is applied
in the partial pipe 12c, whilst a low pressure is present in the
partial pipe 12a. On the other hand, also the volume flows of
blow-by gases from the crankcase are very high in full load
operation. In this case, the non-return valve 6 closes the pipe 16
so that the high pressure in the partial pipe 12c does not act on
the oil separator 20. On the other hand, the low pressure in the
partial pipe 12a suffices to suction off the blow-by gases in full
load operation via the gas output chamber 25.
[0065] FIGS. 1C, 1A and 1B illustrate, in this sequence, also the
development of the states of the device according to the invention
in transition from full load operation, via partial load operation,
to coasting operation. Whilst in full load operation of FIG. 1C the
non-return valve 6 is closed and the valve flaps of the first gas
passage openings are opened, the non-return valve 6 in the
ventilation pipe 16 is opened in the case of suitable pressure
ratios during transition into partial load operation so that the
blow-by gases can be suctioned off completely via the completely
opened gas passage openings in the base plate 35. With further
decreasing power of the engine, i.e. in the further transition to
partial load operation, firstly a first valve flap is then closed,
see FIG. 1A, before, with further decreasing power and transition
to coasting operation, also the second valve flap is closed, see
FIG. 1B.
[0066] In total, it is possible, due to the device according to the
invention, disposed in an internal combustion engine as in the
present FIG. 1, also to enable, in coasting operation of the
internal combustion engine, sufficient suctioning-off of the
blow-by gases without however supplying too large a quantity of
uncombusted hydrocarbons to the catalyst.
[0067] FIG. 2 now shows a device according to the invention in
partial drawings 2A to 2E. This has two partial base plates 35a,
35b which together form the base plate 35.
[0068] The partial base plates 35a and 35b have regions assigned to
each other which have respectively four passage openings 40, 40',
40b, 40b'. These passage openings in both partial base plates 35a
and 35b are disposed in pairs flush with each other, so that they
enable a gas passage from the one side of the double-plate
arrangement to the other side of the double-plate arrangement. In
each of the regions, four gas passage openings are disposed. These
gas passage openings 40 are closable respectively by a valve flap
50, 50' disposed on the pressure side. Each of the valve flaps 50,
50' has respectively one resilient tongue 51, 51' which is mounted,
on one side, via a retaining arm 57 or 57' on an attachment element
56 or 56' on the pressure-side partial base plate 35a. The
retaining arms have first bending points 58 or 58' and second
bending points 59 or 59' (see FIG. 2D) so that the resilient tongue
51 or 51' can be lowered in a planar manner onto the gas passage
openings 40 or 40' and consequently closes these.
[0069] The gas passage openings 40, 40' have a respectively
circumferential web 41, 41', the webs of the gas passage openings
40, 40' being connected together to form a block in respectively
one region, which block protrudes from the plane of the partial
base plate 35a.
[0070] As is shown in FIG. 1C, the valve 6 is closed in full load
operation so that the blow-by gases are supplied completely via the
full load train, i.e. the oil separator, not described further, of
the full load train and the chamber 25 and the output pipe 15 to
the intake duct 10. Hence the same pressure prevails on both sides
of the valve 30, the resilient tongues 51 or 51' are hence in
equilibrium in full load operation. FIG. 2A makes it clear that the
two retaining arms 57 and 57' have different angles and the two
resilient tongues 51 and 51' have different spacings relative to
the surfaces of the webs 41. This is achieved via a different
pre-deformation of the retaining arms 57 or 57'. As a result, it
becomes clear that the two resilient tongues 51 and 51' are
provided with different pretensions.
[0071] The corresponding gas passage openings in the partial base
plate 35b likewise have a circumferential web which protrudes from
the surface of the partial base plate 35b, forming a common
protruding block in the same manner.
[0072] Adjacent to both regions with respectively four gas passage
openings 40 or 40' are further gas passage openings 60, 60' or 60b,
60b' in the plane of the partial base plates 35a or 35b, which
openings extend likewise over the entire arrangement of the partial
base plates 35a, 35b from the pressure side thereof to the suction
side. These gas passage openings 60, 60', 60b, 60b' are unclosable
so that they ensure furthermore a minimum gas throughput in
coasting operation, even with closure of both valve flaps 50,
50'.
[0073] FIG. 2A represents a state in which both valve flaps 50, 50'
are opened corresponding to FIG. 1C.
[0074] FIG. 2B represents a state in which the resilient tongue 51'
is supported on the associated gas passage openings 40' covered by
it and thus the valve flap 50' is closed. The adjacent valve flap
50 is opened, however, because of the higher applied pressure, the
spacing between the surface of the block and the valve flap 50
being smaller than in the state illustrated in FIG. 2A. The state
shown in FIG. 2B corresponds to FIG. 1A in partial load
operation.
[0075] FIG. 2C shows a state in which both valve flaps 50, 50'
close the assigned gas passage openings 40, 40' covered by them. In
this way, only the gas passage openings 60, 60' or 60b, 60b' are
still available for a gas passage of blow-by gases, mixed in
particular with (little) fresh air, with a high proportion of
uncombusted hydrocarbons from the suction side to the pressure
side. These ensure the required ventilation of the crankcase in
coasting operation of the internal combustion engine and, at the
same time, limit the volume flow via the valve 30 and hence the
supply of uncombusted hydrocarbons to the catalyst.
[0076] The resilient tongues, 51, 51' are pretensioned such that
they are opened without applying a pressure difference between the
pressure side (at the top in the drawing) and the suction side (at
the bottom in the drawing). Only if the low pressure applied on the
suction side exceeds a threshold value (i.e. the pressure on the
suction side decreases greatly), is the resilient tongue 51', as
shown in FIGS. 2A to 2C, moved to the surface of the gas passage
openings 40' and closes these. If the low pressure on the suction
side increases further and exceeds a further threshold value, then
the resilient tongue 51 also closes the gas passage openings 40.
The resilient tongues are therefore configured such that they
transition into the closed state in the case of different low
pressures on the suction side of the valve 30. This enables gradual
closing of the gas passage openings and consequently enables
gradual adaptation of the blow-by volume flow via the valve 30 to
the variable low pressure ratios on the suction side of the valve
30. The use of more than two valve flaps enables finer graduation
of the switching behaviour of the valve 30 and control of the
pressure of the blow-by gas.
[0077] FIG. 2D shows a plan view on the partial base plate 35a. The
resilient tongues 51, 51' are mounted on attachment elements 56 or
56' via retaining arms 57 or 57'. The retaining arms 57 or 57' have
first bending points 58, 58' and second bending points 59, 59'.
With the help of these bending points, a movable mounting of the
resilient tongues on the partial base plate 35a is possible. In the
gas passage openings 60, 60', guiding geometries respectively which
direct the blow-by gas flow flowing through these gas passage
openings are situated.
[0078] In FIG. 2E, a plan view on the partial base plate 35b, i.e.
a view from below on the valve 30 in FIG. 2A, is illustrated. In
the gas passage openings 40b, 40b' and also in the additional gas
passage openings 60b, 60b', there are likewise situated
respectively guiding geometries which direct the blow-by gas flow
flowing through the gas passage openings.
[0079] These described guiding geometries are denoted with 42, 42b,
42b', 42b'' and, in the present example of FIG. 2, have the shape
of a half right- or left screw.
[0080] As a result, the gases guided through the gas passage
openings are set in a rotational movement, which reinforces the
separation performance of the respective gas passage openings 40b,
40b', 60, 60', 60b and 60b'. A particularly high separation
performance is achieved if the guiding geometries in the gas
passage openings 60, 60' and also 60b, 60b' are configured such
that the direction of rotation of the gases changes abruptly during
transition from the gas passage openings 60, 60' into the gas
passage opening 60b, 60b'. This can be effected by the direction of
rotation of the associated guiding geometries in the gas passage
openings 60, 60' being in opposite directions to the direction of
rotation of the guiding geometries in the gas passage openings 60b,
60b'. Such guiding geometries can also be disposed in the gas
passage openings 40, 40'.
[0081] FIG. 3 shows, in the partial FIGS. 3A to 3E, a further
embodiment of a valve 30. In contrast to the embodiment in FIGS. 2A
to 2E, now the resilient tongues 51, 51' are mounted respectively
via two retaining arms 57, 57'. This enables uniform guidance of
the resilient tongues 51, 51'. The two retaining arms 57 of the
block of gas passage openings 40, disposed further to the left, are
both the same and in fact are more strongly pre-deformed than the
two retaining arms 57' of the block of gas passage openings 40',
disposed further to the right. As a result, the left resilient
tongue 51 has greater pretension than the right resilient tongue
51'.
[0082] In contrast to FIG. 2, now merely the gas passage openings
40b' have guiding geometries, whilst the gas passage openings 40b
and also 60, 60', 60b, 60b' comprise no corresponding guiding
geometries.
[0083] FIG. 4 shows a further embodiment of the valve 30. In
contrast to FIG. 2, each region with gas passage openings now has
eight gas passage openings. The associated resilient tongues 51,
51' are manufactured as a one-part component and are mounted on a
common central web. This central web 55 is attached to attachment
means 56, 56', for example pins 56, 56' protruding out of the
partial base plate 35a. The retaining arms 57 have a substantially
narrower configuration than the retaining arms 57' so that the
retaining arms 57, in the case of the same pre-deformation of the
retaining arms 57 and 57', which is not explicitly detectable here
in the closed state, have less pretension.
[0084] Furthermore, the partial base plate 35a has an unclosable
gas passage opening 60.
[0085] FIG. 5 shows a further embodiment of a valve according to
the invention, FIG. 5A again showing a plan view on the valve 30,
i.e. a plan view on a base plate 35, FIG. 5B a side view and FIG.
5C a view from below of the valve 30, i.e. a plan view on the base
plate 35.
[0086] Also in this embodiment, two regions which have respectively
eight gas passage openings in the base plate 35 are provided. The
resilient tongues 51, 51' are disposed offset relative to each
other so that the constructional space on the base plate 35 is well
exploited.
[0087] Both valve closures 50, 50' have respectively only one
retaining arm 57, 57'. The retaining arm 57' is essentially
narrower and configured with a greater radius than the retaining
arm 57 so that the retaining arm 57', in the case of the same
pre-deformation of the retaining arms 57 and 57', which is not
explicitly detectable here in the plan view in the closed state,
has less pretension than the retaining arm 57.
[0088] In contrast to the preceding embodiments, one of the
resilient tongues, here the resilient tongue 51, has an opening 53
which is disposed directly above a gas passage opening in the
partial base plate 35a and a gas passage opening situated
thereunder in the partial base plate 35b. The corresponding gas
passage opening in the partial base plate 35b is denoted with X in
FIG. 5C. The gas passage opening 53 in the resilient tongue 51
prevents the gas passage opening situated thereunder from being
able to be closed. This gas passage opening serves therefore for
maintaining a minimum gas throughput in coasting operation, in the
same manner as the unclosable gas passage openings 60, 60', 60b,
60b' in the other preceding examples.
[0089] FIG. 5B illustrates the valve 30 in the closed state of both
valve flaps 50, 50' in a side view on the side of the valve 30
pointing downwards in FIG. 5A. Both resilient tongues 51, 51' are
pretensioned and protrude externally upwards away from the base
plate 35. The groups of passage openings 40, 40' have, on the
pressure side pointing upwards, respectively one web 62 or 62'
which extends circumferentially about the entire group and forms
respectively a support for the resilient tongue 51 or 51'. This web
62 or 62' has, along the circumference thereof, a changing,
increasing height, namely with increasing distance from the
respective attachment means 56 or 56'. If the angles at which the
pretensioned resilient tongues 51, 51', on the one hand, and the
upper edge of the web 62 or 62', on the other hand, extend relative
to the plane of the base plate 35 are compared, then a greater
angle results for the resilient tongues 51, 51'. This means that
the resilient tongues 51, 51' are bent before complete closure of
the passage openings 40, 40' against the pretension of the
resilient tongues 51, 51'.
[0090] FIG. 6 shows a further embodiment of a device according to
the invention with reference to a side view comparable to FIG. 5B,
likewise in the opened state. The resilient tongues 51, 51' are
designed here without pre-deformation. The pretension of the flap
of the resilient tongues 51, 51' is produced via the web 62, 62'
which, similarly to the embodiment of FIG. 5, has a
circumferentially changing height, here the height reducing with
increasing spacing relative to the attachment means 56, 56' of the
associated resilient tongue 51, 51'. Upon closure of the resilient
tongues 51, 51', these abut firstly against the portion of the edge
62, 62' which points towards the centre of the illustrated side
view and, in the further course, against the pretension which is
produced from the straight shape of the spring-hardened steel plate
of the resilient tongues 51, 51', unwind on the edge and thus close
the passage opening 40, 40'.
[0091] Furthermore, the resilient tongues 51, 51' have sealing
elements 69 which extend circumferentially on the lower side
thereof and are configured as elastomer beads.
[0092] FIG. 7 shows, in the partial Figures A, A', B, B', C, C', a
further embodiment of a device according to the invention with
reference to side views A, B and C and also corresponding plan
views A', B', C'. In FIGS. 7A, 7A', the valve is illustrated in the
completely closed state, in FIGS. 7B, 7B' in a specifically
pretensioned state and, in FIGS. 7C, 7C', in an opened state.
[0093] FIG. 7 shows a valve 1 with gas passage openings 40, 60a and
60b. The gas passage openings 60a and 60b are unclosable and
therefore serve as bypass from the pressure side to the suction
side of the valve 1. The gas passage opening 40 is closed by a
resilient tongue 51 as valve flap 50 in FIGS. 7A, 7A'. The
resilient tongue 51 is connected to the base plate 35 of the valve
1 via a retaining arm 57 on an attachment element 56.
[0094] The retaining arm 57 has, between the attachment point 56
and the resilient tongue 51, two bending points 70, 71 (bends), at
which the retaining arm 57 is bent in different directions. In
FIGS. 7C, 7C', which show the valve in the opened state in the case
of a small pressure difference between the pressure side and the
suction side of the valve 1, the resilient tongue 51 is at a
spacing completely from the gas passage opening 40 or the wall
thereof. As a result, a large gap between the wall of the gas
passage opening 40 and the resilient tongue 51 is produced so that
a large volume flow can flow through the gas passage opening 40 in
the case of a small pressure difference.
[0095] If the low pressure on the suction side of the valve 1 is
increased, which is present here in the drawing plane below the
base plate 35, then the resilient tongue 51 is suctioned towards
the gas passage opening 40. This takes place until the resilient
tongue 51 abuts on the wall of the gas passage opening 40 with the
region situated opposite the gas passage opening 40. In fact the
flow gap between the gas passage opening 40 and the resilient
tongue 51 is thereby reduced so that the volume flow which can flow
through this gap is reduced. At the same time, the flow resistance
decreasing over the valve 1 is increased so that in fact a
crankcase is protected here if necessary from low pressure which is
too low in the intake duct of an internal combustion engine.
[0096] If the low pressure on the suction side of the valve 1
increases further, then, finally, as illustrated in FIGS. 7A, 7A',
the resilient tongue 41 is suctioned towards the surface of the
wall of the gas passage opening 40 so that the latter is completely
closed by the resilient tongue 51. As gas passage openings, there
remain then merely the unclosable openings 60a and 60b which ensure
sufficient suctioning of the blow-by gases out of the crankcase and
sufficient oil separation. In order to close the gas passage
opening 40 completely by the resilient tongue 51, bending of the
region of the resilient tongue 51 situated opposite the gas passage
opening 40 is effected about a bending point 71.
[0097] Upon reducing the low pressure on the suction side of the
valve 1, now the previously described steps for closing the gas
passage opening 40 are run through in reverse sequence to FIGS. 7A,
7A', via FIGS. 7B, 7B', to FIGS. 7C, 7C'. In fact a low pressure
difference thereby suffices for opening of the valve flap 50.
[0098] FIG. 8 illustrates, in a side view and a plan view, a
further device according to the invention with a valve 1 and gas
passage openings 40, 60a and 60b. The gas passage openings 40, 60a
and 60b are thereby designed as in the preceding embodiment. The
embodiment of FIG. 8 differs from that of FIG. 7, on the one hand,
by the valve flap 50 here being embedded directly in a continuation
63 of a web 41 which extends circumferentially about the gas
passage openings 40. This continuation 63 is formed in one piece
and materially uniform with the base plate 35, but has a greater
total height than the webs 41. The resilient tongue 51 is thereby
embedded at a rising angle coordinated to the spacing from the edge
so that, in the opened state illustrated here, a pretension is
produced. The switching behaviour of the valve 30 hence corresponds
here extensively to that of the valve from the embodiment of FIG. 7
between the states of partial FIGS. 7A and 7B so that, here also, a
low pressure difference leads to opening of the valve flap 50.
* * * * *