U.S. patent application number 14/195093 was filed with the patent office on 2014-06-26 for device for providing liquid reducing agent and motor vehicle having the device.
This patent application is currently assigned to Emitec Gesellschaft Fuer Emissionstechnologie MBH. The applicant listed for this patent is Emitec Gesellschaft Fuer Emissionstechnologie MBH. Invention is credited to JAN HODGSON, GEORGES MAGUIN, SVEN SCHEPERS.
Application Number | 20140174058 14/195093 |
Document ID | / |
Family ID | 46704694 |
Filed Date | 2014-06-26 |
United States Patent
Application |
20140174058 |
Kind Code |
A1 |
MAGUIN; GEORGES ; et
al. |
June 26, 2014 |
DEVICE FOR PROVIDING LIQUID REDUCING AGENT AND MOTOR VEHICLE HAVING
THE DEVICE
Abstract
A device for providing liquid reducing agent for an exhaust-gas
treatment device includes a tank and a delivery unit with an intake
or suction point in the tank at which reducing agent can be
suctioned or drawn out of the tank. The intake point is covered by
a separation layer in such a way that a closed intermediate space
is formed between the intake point and the separation layer. The
separation layer has a higher flow resistance to reducing agent in
an outflow direction from the intermediate space into the tank than
in an inflow direction from the tank into the intermediate space. A
motor vehicle having the device is also provided.
Inventors: |
MAGUIN; GEORGES; (MARLY,
FR) ; SCHEPERS; SVEN; (TROISDORF, DE) ;
HODGSON; JAN; (TROISDORF, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Emitec Gesellschaft Fuer Emissionstechnologie MBH |
Lohmar |
|
DE |
|
|
Assignee: |
Emitec Gesellschaft Fuer
Emissionstechnologie MBH
Lohmar
DE
|
Family ID: |
46704694 |
Appl. No.: |
14/195093 |
Filed: |
March 3, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2012/066363 |
Aug 22, 2012 |
|
|
|
14195093 |
|
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Current U.S.
Class: |
60/282 ;
422/168 |
Current CPC
Class: |
F01N 2610/1426 20130101;
Y02T 10/24 20130101; Y02T 10/12 20130101; F01N 2610/1406 20130101;
Y02A 50/2325 20180101; F01N 2610/02 20130101; F01N 3/206 20130101;
Y02A 50/20 20180101; F01N 3/2066 20130101 |
Class at
Publication: |
60/282 ;
422/168 |
International
Class: |
F01N 3/20 20060101
F01N003/20 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 2, 2011 |
DE |
102011112325.7 |
Claims
1. A device for providing liquid reducing agent for an exhaust-gas
treatment device, the device comprising: a tank; a delivery unit
having an intake point disposed in said tank and configured to
draw-in reducing agent from said tank; and a partition layer
covering said intake point, forming a closed intermediate space
between said intake point and said partition layer and defining an
outflow direction from said intermediate space into said tank and
an inflow direction from said tank into said intermediate space;
said partition layer having a higher flow resistance for reducing
agent in said outflow direction than in said inflow direction.
2. The device according to claim 1, wherein said partition layer is
unidirectionally permeable to reducing agent in said inflow
direction at least up to a threshold pressure difference of 0.01
bar to 0.1 bar between said tank and said intermediate space.
3. The device according to claim 1, wherein said partition layer is
a filter having at least one barrier ply increasing said flow
resistance of said partition layer in said outflow direction.
4. The device according to claim 1, wherein said partition layer is
a screen having at least one flow-impeding device increasing said
flow resistance of said partition layer in said outflow
direction.
5. The device according to claim 1, which further comprises a
chamber disposed at least partially in said tank, said delivery
unit being disposed in said chamber, and said partition layer
surrounding said chamber and forming said intermediate space as an
encircling intermediate space between said chamber and said
partition layer.
6. The device according to claim 1, which further comprises at
least one guide structure disposed in said tank around said
partition layer and configured to guide the reducing agent toward
said partition layer.
7. The device according to claim 1, wherein said partition layer is
permeable to air bubbles in said outflow direction out of said
intermediate space.
8. The device according to claim 1, wherein said partition layer is
configured to promote a flow of heat in said inflow direction and
reduce a flow of heat in said outflow direction.
9. The device according to claim 1, wherein said partition layer
has a support structure imparting stability to said partition
layer, and said support structure has a negligible flow resistance
for reducing agent in said inflow direction and in said outflow
direction.
10. A motor vehicle, comprising: an internal combustion engine; an
exhaust-gas treatment device for purification of exhaust gases of
said internal combustion engine; and a device according to claim 1
for supplying reducing agent to said exhaust-gas treatment device.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation, under 35 U.S.C. .sctn.120, of
copending International Application No. PCT/EP2012/066363, filed
Aug. 22, 2012, which designated the United States; this application
also claims the priority, under 35 U.S.C. .sctn.119, of German
Patent Application DE 10 2011 112 325.7, filed Sep. 2, 2011; the
prior applications are herewith incorporated by reference in their
entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The invention relates to a device for providing liquid
reducing agent for an exhaust-gas treatment device and a motor
vehicle having the device.
[0003] In the automotive field in particular, widespread use is
made of exhaust-gas treatment devices into which an additional
substance is fed for the purification of the exhaust gas of an
internal combustion engine. An exhaust-gas purification method
particularly widely used in such exhaust-gas treatment devices is
the process of selective catalytic reduction (the SCR process). In
that method, a reducing agent is supplied to the exhaust gas.
Nitrogen oxide compounds in the exhaust gas can be reduced by the
reducing agent. Ammonia is generally used as reducing agent.
Ammonia is normally not stored in motor vehicles directly but
rather in the form of a precursor solution which can be converted
to form ammonia. The conversion may be performed within the
exhaust-gas treatment device and/or in an additional reactor
provided for that purpose. The reactor may be disposed in the
exhaust line and/or outside the exhaust line. An aqueous urea
solution may be used, for example, as a reducing agent precursor. A
32.5% urea-water solution is available as a reducing agent
precursor under the trademark AdBlue.RTM.. The expressions
"reducing agent" and "reducing agent precursor solution" and
"reducing agent precursor" will hereinafter be used synonymously
for one another.
[0004] In order to provide the reducing agent for an exhaust-gas
treatment device in a motor vehicle, a tank is normally provided
for the reducing agent and a delivery unit is provided for
delivering the reducing agent from the tank to the exhaust-gas
treatment device. The tank and the delivery unit should be as
inexpensive as possible, and should at the same time ensure
reliable provision of the reducing agent. It has proven to be a
problem, in particular, that the reducing agent in the tank
contains impurities that can cause damage to the delivery unit or
to an injector for the injection of the reducing agent into the
exhaust-gas treatment device. A delivery unit therefore typically
has a filter by which impurities in the reducing agent can be
retained.
SUMMARY OF THE INVENTION
[0005] It is accordingly an object of the invention to provide a
device for providing liquid reducing agent and a motor vehicle
having the device, which overcome the hereinafore-mentioned
disadvantages and solve or at least alleviate the highlighted
technical problems of the heretofore-known devices and vehicles of
this general type. It is sought, in particular, to provide a
particularly inexpensive device for the reliable provision of
liquid reducing agent for an exhaust-gas treatment device.
[0006] With the foregoing and other objects in view there is
provided, in accordance with the invention, a device for providing
liquid reducing agent for an exhaust-gas treatment device,
comprising a tank and a delivery unit with an intake or suction
point in the tank at which reducing agent can be drawn-in from the
tank. The intake point is covered by a partition layer in such a
way that a closed intermediate space is provided between the intake
point and the partition layer. The partition layer has a higher
flow resistance for reducing agent in an outflow direction from the
intermediate space into the tank than in an inflow direction from
the tank into the intermediate space.
[0007] The intake point in the tank is preferably an opening in the
wall of the tank. The opening is adjoined by a line which leads to
the delivery unit. It is likewise possible for the intake point to
be formed correspondingly on a delivery unit housing, which
projects into the tank. The partition layer preferably forms a type
of cover over the intake point. The partition layer may be
constructed, for example, in the manner of a dome that is placed
over the intake point. It is also possible for the intake point to
be situated in a recess of the tank or in a recess of the tank
wall, and for the partition layer to close off or cover that
recess. In other words, the partition layer preferably spans the
intake point.
[0008] The intermediate space is preferably situated between the
partition layer and a tank wall in the region of the intake point.
The flow resistance for reducing agent in the inflow direction or
in the outflow direction is defined by the flow rate of reducing
agent that can pass through the partition layer in the presence of
a predefined pressure difference. The flow resistance need not be
constant in the case of different pressure differences between the
intermediate space and the tank. It is also possible for flow
resistance to vary as a function of the pressure difference. Within
the context of the invention, it is preferable for the flow
resistance in the outflow direction to be significantly increased
in relation to the flow resistance in the inflow direction, in
particular, in the range of low pressures (pressures up to 0.2 bar
and, in particular, pressures up to 0.1 bar). A pressure of 0.2 bar
corresponds to a water column of 2 m [meters], and a pressure of
0.1 bar corresponds to a water column of 1 m [meter]. Pressures
higher than that do not normally arise between the tank and the
intermediate space. The pressure difference between the
intermediate space and the tank is determined substantially by the
mass flow of reducing agent through the partition layer and by the
liquid levels in the intermediate space and in the tank, and also
by the impact of the liquid in the case of sloshing movements in
the tank and in the intermediate space. In the case of those
effects, it is the case, in particular, that the fraction of the
pressure difference arising from the occurring mass flow of
reducing agent is negligible. Accordingly, the occurring pressure
differences are determined substantially by the structural size of
the tank, and very rarely exceed the value of 0.2 bar mentioned
further above. Therefore, for the function of the partition layer,
the way in which that partition layer behaves in the presence of
relatively high pressure differences is less relevant. For example,
it is possible for the flow resistances of the partition layer in
the inflow direction and in the outflow direction to converge on
one another again, or to fully equalize, in the presence of
pressure differences of greater than 0.2.
[0009] Through the use of such a differing configuration of the
flow resistances in the inflow direction and outflow direction, it
can be ensured in regular operation that reducing agent that has
passed through the partition layer into the intermediate space does
not flow back, or flows back again only to a limited extent, into
the tank.
[0010] A partition layer serves, in particular, to realize a
spatial division of the intermediate space from the rest of the
tank volume, which serves for example as an intermediate
accumulator or reservoir for the delivery unit. The reducing agent
situated therein may exhibit different properties (for example
different cleanliness or different purity) than the reducing agent
in the remainder of the tank.
[0011] The partition layer may also be equipped with a heater by
which the reducing agent in the vicinity, in particular in the
intermediate space, can be heated. The heater may, for example,
include at least one heating element (in particular PTC heating
elements) which is incorporated into the partition layer. For
example, heating wires may be woven into the partition layer. The
heater may also be constructed to heat the reducing agent in the
tank, but the heater should serve primarily to heat the reducing
agent in the intermediate space. The heat output by the heater is
preferably initially output primarily into the intermediate space.
When the reducing agent in the intermediate space is in liquid
form, the heat from the heater also passes into the tank. For this
purpose, the heater is preferably provided on an inner side, facing
toward the intermediate space, of the partition layer.
[0012] The partition layer may preferably perform multiple or
different functions during the provision of reducing agent, such as
filtering, screening, heating or the like.
[0013] The partition layer may also have a fill level sensor for
measuring the fill level in the tank. The fill level sensor may,
for example, be in the form of electrical contacts that are
fastened to the partition layer. It is likewise possible for the
temperature to be inferred by checking the electrical resistance of
a component (in particular of a heating element) of the partition
layer.
[0014] In accordance with another advantageous feature of the
device of the invention, the partition layer is only
unidirectionally permeable to reducing agent in the inflow
direction at least up to a threshold pressure difference of 0.01
bar to 0.1 bar between the tank and the intermediate space.
[0015] Through the use of such a configuration of the partition
layer, it is possible, at least in the range of pressure
differences that arise between the tank and intermediate space
during regular operation, to completely prevent reducing agent from
flowing from the intermediate space back into the tank. The action
of the partition layer is thus particularly effective.
[0016] A partition layer of this type may be a semi-permeable
structure, that is to say in other words, in particular, a
structure which is semi-permeable, that is to say which allows only
certain substances (reducing agent fractions) to pass through
and/or allows substances to pass through in only one (single)
direction. The diaphragm may, for example, include multiple layers
of a textile fabric, wherein in particular, a Teflon.RTM. layer
(polytetrafluoroethylene) is provided.
[0017] A partition layer of this type may be composed of a
combination of a filter ply/screen ply with a sponge on the
filtered side (in the present case on the inner side). The sponge
may be in the form of a thin sponge ply that bears against the
filter ply/screen ply and/or is fixedly connected to the filter
ply/screen ply. The sponge ply is preferably thinner than 2 mm
[millimeters] and is particularly preferably thinner than 1 mm.
Capillary forces act in the sponge or in the sponge ply. The
partition layer retains a volume of reducing agent due to the
capillary forces. A barrier ply is thus formed which prevents a
backflow of the reducing agent through the filter ply/screen
ply.
[0018] In accordance with a further advantageous feature of the
device of the invention, the partition layer is a filter which has
at least one barrier ply that increases the flow resistance of the
partition layer in the outflow direction.
[0019] The barrier ply imparts a barrier action in the outflow
direction at least in the range of low pressure differences between
the intermediate space and the tank. This means that the barrier
ply prevents a flow of reducing agent out of the tank.
[0020] A barrier ply of this type may also be formed with a
suitable semi-permeable structure. A barrier ply may, if
appropriate, also have a multi-layer form in order to ensure an
improved barrier action.
[0021] The partition layer may thus have a filtering action.
Reducing agent flowing into the intermediate space is filtered. It
is thus possible for impurities in the reducing agent in the tank
to be kept away from the intake point. Impurities are prevented
from passing into the intermediate space and to the intake point.
At the same time, as a result of the increased flow resistance in
the outflow direction, it is ensured that reducing agent that has
already been filtered does not pass out of the intermediate space
back into the tank. It is thus possible to prevent reducing agent
from being filtered twice. At the same time, a reservoir of
filtered reducing agent is situated in each case in the
intermediate space in the direct vicinity of the intake point.
[0022] The barrier action and the filtering action may be realized
in two different plies of the partition layer. Then, in addition to
the barrier ply, there is preferably also provided a filter ply
that performs the filtering action. The partition layer is then of
multi-layer form. The barrier ply and the filter ply may also be
realized in a common ply which combines the described barrier
action and the described filtering action with one another. The
combined filter ply and barrier ply may, for example, have pores
and/or ducts which (under normal operating conditions) are
permeable to reducing agent, and retain particles that are larger
than the pores or ducts, in the inflow direction, and which are
permeable neither to reducing agent nor to such particles in the
outflow direction.
[0023] In accordance with an added feature of the device of the
invention, the partition layer is a screen which has at least one
flow-impeding device that increases the flow resistance of the
partition layer in the outflow direction.
[0024] Through the use of a screen, it is likewise possible for
reducing agent to be purified as it passes out of the tank into the
intermediate space. A screen has openings of a uniform size. The
openings may, for example, have a uniform diameter of less than 1
mm [millimeter], preferably of less than 0.5 mm [millimeters] and
particularly preferably of between 10 .mu.m [micrometers] and 20
.mu.m. Through the use of a screen, particles in the reducing agent
can be retained in such a way that they do not pass into the
intermediate space and thus also do not pass to the intake point.
In order to increase the flow resistance from the intermediate
space back into the tank, it is possible, in the case of the
embodiment of the partition layer as a screen, for at least one
flow-impeding device to be provided. Flow-impeding devices may, for
example, be valve devices which close the openings of the screen
upon the onset of a backflow from the intermediate space into the
tank (in the outflow direction). Flow-impeding devices or valve
devices may, for example, be movable vanes which are fastened to
the screen on one side and which cover the openings of the screen
in the case of a flow proceeding from that side of the screen which
has the vanes. In the case of the partition layer in the form of a
screen in the described device, the vanes are preferably fastened
to that side of the screen which faces the intermediate space. A
backflow from the intermediate space into the tank (in the outflow
direction) can be prevented in an effective manner by the
vanes.
[0025] In accordance with an additional advantageous feature of the
device of the invention, the delivery unit is disposed in a chamber
which is disposed at least partially in the tank, and the partition
layer surrounds the chamber in such a way that an encircling
intermediate space is provided between the chamber and the
partition layer.
[0026] The partition layer surrounds the chamber preferably in a
radially encircling manner in such a way that, for example, an
encircling, in particular annular intermediate space is provided
between the chamber and the partition layer. The chamber is
preferably a constituent part of the tank bottom. The chamber
preferably extends upward into the tank volume from the tank
bottom. The chamber, however, extends preferably at most over 30%,
and particularly preferably at most over 15%, of the tank height.
In the case of this type of construction, the intake point may be
situated on the chamber and thus in the direct vicinity of the
delivery unit and simultaneously in the vicinity of the tank
bottom, in such a way that the reducing agent can be drawn in from
the tank through the intake point as completely as possible.
[0027] A spacer structure may also be provided between the chamber
and the partition layer for ensuring spacing between the chamber
and the partition layer. It is thus possible for an adequately
large reservoir for filtered reducing agent to be provided between
the chamber and the partition layer. Due to the properties of the
partition layer, the reducing agent does not flow out of the
reservoir back into the tank, or flows out of the reservoir back
into the tank only in a time-delayed manner. It can thus be
achieved that reducing agent is available at the intake point in
each case during cornering and in the event of sloshing movements
in the tank.
[0028] In accordance with yet another advantageous feature of the
device of the invention, at least one guide structure is disposed
in the tank around the partition layer, which guide structure
guides the reducing agent toward the partition layer.
[0029] The guide structure may, for example, be in the form of
guide plates that guide the reducing agent toward the partition
layer if the tank is in an oblique position or in the event of
sloshing movements in the tank. It can thus be achieved that the
reducing agent in the tank collects in front of the outside of the
partition layer and is conducted into the intermediate space. Due
to the increased flow resistance in the outflow direction, the
reducing agent does not flow out of the intermediate space again,
or flows out of the intermediate space again only at a
significantly slower rate. Thus, even if the tank is in an oblique
position or in the event of sloshing movements in the tank, an
amount of reducing agent remains in each case in the intermediate
space in the direct vicinity of the intake point, in such a way
that the delivery of reducing agent by using the delivery unit is
not interrupted. This is the case even if the reducing agent fill
level in the tank is already greatly depleted.
[0030] In accordance with yet a further advantageous feature of the
device of the invention, the partition layer is permeable to air
bubbles in the outflow direction from the intermediate space. It is
thus possible for air bubbles to be prevented from collecting in
the intermediate space. Suitable semi-permeable materials that are
permeable to reducing agent only in one direction and which thus
act as a barrier ply may be permeable to air bidirectionally, that
is to say in both directions. With diaphragms composed of materials
of this type, it is possible to realize permeability of the
partition layer to air bubbles.
[0031] In accordance with yet an added advantageous feature of the
device of the invention, the partition layer promotes a flow of
heat in the inflow direction and reduces the flow of heat in the
outflow direction.
[0032] It is thus possible to prevent a situation in which, when
freezing occurs, the reducing agent in the intermediate space
freezes more quickly than that in the tank. It is preferable for
liquid reducing agent to remain in the intermediate space when the
reducing agent in the tank has already frozen. It is thus possible
to realize a situation in which, upon start-up of the delivery
unit, liquid reducing agent may be directly present at the intake
point even though the reducing agent in the tank is largely frozen.
It is therefore not necessary for the intermediate space to be
initially melted free by using a heater.
[0033] In accordance with yet an additional advantageous feature of
the device of the invention, the partition layer has a support
structure which imparts stability to the partition layer, wherein
the flow resistance of the support structure for reducing agent is
negligible in the inflow direction and in the outflow
direction.
[0034] The flow resistance is, in particular, negligible in
relation to the flow resistance of further plies of the partition
layer. The support structure thus exhibits practically no relevant
filtering action and rather serves merely to predefine the shape
and position of the partition layer. The support structure may, for
example, be implemented as a sheet-metal construction which
surrounds the further plies of the partition layer and/or to which
the further plies of the partition layer are applied. The support
structure may, for example, form at least one frame for the
partition layer. The support structure may be in the form of a
framework construction which spans a beam-type skeleton to which
the further plies of the partition layer can be applied. A support
structure is advantageous, in particular, if the partition layer
includes a filter, because a filter normally exhibits relatively
low mechanical stability and the filter can thus be held in
position, and/or in the intended shape, in particularly
advantageous fashion by using a support structure. The support
structure and further plies (for example a filter ply, a heat
protection ply and/or a barrier ply) of the partition layer may
also be connected to one another. It is, for example, possible for
the support structure to partially extend through further plies of
the partition layer and/or to penetrate partially into further
plies of the partition layer and for the support structure to
thereby mechanically hold further plies of the partition layer.
Further plies of the partition layer may also be welded or
adhesively bonded to the support structure. The connection between
the partition layer and the support structure may also be formed in
linear regions (for example at the edges of the partition layer)
and/or areally.
[0035] In a further advantageous embodiment of the device, the
properties of the partition layer vary over the area of the
partition layer. This means, in particular, that the partition
layer has varying properties at least in sections. It is preferable
for the area of the partition layer to be divided into at least two
zones, wherein the properties of the partition layer are different
in the zones. It is also possible for the properties of the
partition layer to vary in continuous fashion as viewed over the
area of the partition layer.
[0036] In this case, "properties of the partition layer" refers to
the properties already described further above, such as for example
the unidirectional permeability or the bidirectional permeability
of the partition layer to reducing agent and/or to air, or the flow
resistance of the partition layer for reducing agent and/or for air
in the inflow direction and in the outflow direction.
[0037] It is particularly preferable for the partition layer to
have a first zone and a second zone, wherein (in the intended
installation orientation of the device) the first zone is situated
above the second zone, wherein the partition layer, in the second
zone, has a higher flow resistance for reducing agent in an outflow
direction from the intermediate space into the tank than in an
inflow direction from the tank into the intermediate space, and
wherein the partition layer, in the first zone, has an improved
permeability in relation to the second zone. It is preferable, in
particular, for the first zone to exhibit improved permeability to
air in the outflow direction.
[0038] Furthermore, it is preferable for the partition layer to be
constructed at least partially from a first material in the first
zone and to be constructed at least partially from a second
material in the second zone, wherein the first material and the
second material exhibit different properties, in particular, with
regard to permeability to air and/or to reducing agent. It is
preferable for the second material for the partition layer to not
be used in the first zone and for the first material for the
partition layer to not be used in the second zone. The first
material preferably exhibits improved permeability to air in
relation to the second material. The second material preferably
exhibits different flow resistances for reducing agent in the two
through flow directions (in an inflow direction and in an outflow
direction). The second zone of the partition layer preferably forms
a space in which reducing agent collects during operation of the
device. Air bubbles in the intermediate space between the intake
point and the partition layer can thus escape from the intermediate
space through the first zone.
[0039] With the objects of the invention in view, there is
concomitantly provided a motor vehicle, comprising an internal
combustion engine, an exhaust-gas treatment device for the
purification of the exhaust gases of the internal combustion
engine, and a device which is constructed to supply reducing agent
to the exhaust-gas treatment device. The exhaust gas from the
internal combustion engine flows through the exhaust-gas treatment
device in an exhaust-gas flow direction. The device conducts the
reducing agent to the exhaust-gas treatment device through an
injector. The injector is constructed to inject the reducing agent
into the exhaust-gas treatment device. The injector may either be a
self-opening nozzle or may, by using an actuable valve element,
control the flow rate of reducing agent supplied to the exhaust-gas
treatment device. In the exhaust-gas treatment device there is
disposed an SCR catalytic converter in which the SCR process for
exhaust-gas purification is performed. In this case, nitrogen oxide
compounds in the exhaust gas are converted with the aid of the
reducing agent to form non-hazardous substances such as water,
carbon dioxide and nitrogen.
[0040] It may also be advantageous for at least one fill level
sensor to be disposed and/or integrated in and/or on the partition
layer. The fill level of the reducing agent in the tank can be
monitored by using a fill level sensor. The fill level sensor may
be a continuous fill level sensor which permits permanent
monitoring of the fill level in a range between a minimum
measurable fill level and a maximum measurable fill level. The fill
level sensor may also exhibit discrete characteristics. A discrete
fill level sensor can detect only whether reducing agent is present
at (at least) a certain level in the tank, and the fill level in
the tank is thus above the level monitored by the fill level
sensor. In particular, in the case of discrete fill level sensors,
it is expedient for multiple fill level sensors to be disposed in
and/or on the particle screen. It is thus possible to obtain more
precise information regarding the fill level in the tank.
[0041] The at least one fill level sensor may, for example, be
realized in the form of an electrical conductor and/or in the form
of an electrical contact. The measurement of the fill level may
preferably be performed by using an electrical resistance and/or
electrical capacitance. The electrical resistance and/or electrical
capacitance between two electrical contacts or two electrical
conductors changes as a function of whether or not reducing agent
is present at/between the contacts or at/between the conductors.
This can be utilized for the determination of the fill level. The
electrical contacts and/or the electrical conductors may, for
example, be adhesively bonded, welded and/or soldered or brazed to
the partition layer. At least one ply (support ply, barrier ply,
etc.) of the partition layer may also be implemented as a fabric or
mesh. The electrical contacts and/or electrical conductors may then
be woven or braided into the ply.
[0042] Other features which are considered as characteristic for
the invention are set forth in the appended claims, noting that
features specified individually in the claims may be combined with
one another in any desired technologically meaningful way and may
be supplemented by explanatory facts from the description, with
further embodiments of the invention being highlighted.
[0043] Although the invention is illustrated and described herein
as embodied in a device for providing liquid reducing agent and a
motor vehicle having the device, it is nevertheless not intended to
be limited to the details shown, since various modifications and
structural changes may be made therein without departing from the
spirit of the invention and within the scope and range of
equivalents of the claims.
[0044] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0045] FIG. 1 is a diagrammatic, vertical-sectional view of a first
embodiment of a device for providing liquid reducing agent;
[0046] FIG. 2 is a vertical-sectional view of a second embodiment
of a device for providing liquid reducing agent;
[0047] FIG. 3 is a vertical-sectional view of a third embodiment of
a device for providing liquid reducing agent;
[0048] FIG. 4 is a longitudinal-sectional view of a screen for a
device for providing liquid reducing agent;
[0049] FIG. 5 is a top-plan view of a device for providing liquid
reducing agent;
[0050] FIG. 6 is a block diagram of a motor vehicle having a device
for providing liquid reducing agent; and
[0051] FIG. 7 is a vertical-sectional view of a fourth embodiment
of a device for providing liquid reducing agent.
DETAILED DESCRIPTION OF THE INVENTION
[0052] Referring now in detail to the figures of the drawing for
explaining the invention and the technical field in more detail by
showing particularly preferred structural variants to which the
invention is not restricted, and first, particularly, to FIGS. 1, 2
and 3 thereof, there are seen diagrammatic illustrations of
different embodiments of a device 1 for providing liquid reducing
agent. The various combinations of features of a device of this
type, which are illustrated in each of FIGS. 1, 2 and 3, are merely
exemplary. Features illustrated in the various figures may be
combined with one another as desired and combined with further
features from the description as a whole.
[0053] It is possible in each case to see the device 1, having a
tank 3 in which a reducing agent can be stored as well as a
delivery unit 4 disposed in a chamber 9. The chamber 9 is a
constituent part of a tank bottom 25 or is inserted into the tank
bottom 25. An intake point 5 through which reducing agent can be
drawn-in, is situated on the chamber 9 in the region of the tank
bottom 25. The delivery unit 4 has a pump 17 for drawing-in
reducing agent. The delivery unit 4 and the chamber 9 are
surrounded by a partition layer 6. At the same time, the partition
layer 6 covers the intake point 5, so that an intermediate space 7
is formed between the partition layer 6 and the intake point 5 or
between the partition layer 6 and the delivery unit 4 or between
the partition layer 6 and the chamber 9. There is an inflow
direction 23 from the tank 3 through the partition layer 6 into the
intermediate space 7. Furthermore, there is an outflow direction 24
from the intermediate space 7 through the partition layer 6 back
into the tank 3. Reducing agent drawn-in at the intake point 5 is
made available by the delivery unit 4 at a line connector 16 to
which there can be connected a line through which the reducing
agent can be conducted to an exhaust-gas treatment device.
[0054] FIG. 1 illustrates a partition layer 6 which is a filter 18
having a filter ply 14 for filtering the reducing agent and also a
barrier ply 8 which influences the flow resistance of the partition
layer 6 in such a way that the flow resistance for reducing agent
in the inflow direction 23 is lower than the flow resistance in the
outflow direction 24. Furthermore, the partition layer 6 according
to FIG. 1 has a support structure 11 which holds the partition
layer 6 in its position and/or predefines the shape of the
partition layer 6. The support structure 11 is, for example, in the
form of a perforated metal sheet.
[0055] In FIG. 2, the partition layer 6 has a filter ply 14 and a
heat protection ply 15, in which the heat protection ply 15 is
suitable for reducing the flow of heat in the outflow direction 24,
in such a way that the intermediate space 7 of the device 1 cools
down more slowly and, after a freezing phase in which the reducing
agent in the tank 3 has frozen, liquid reducing agent is, where
possible, still present in the intermediate space 7. Furthermore,
in the embodiment of FIG. 2, a guide structure 10 is illustrated
which ensures that reducing agent passes to the partition layer 6
when the device 1 or the tank 3 is in an oblique position or in the
event of sloshing movements in the tank 3.
[0056] In the embodiment according to FIG. 3, the partition layer 6
is formed with a screen 19 which is constructed so as to hinder the
flow of reducing agent in the outflow direction 24 and facilitate
the flow of reducing agent in the inflow direction 23.
[0057] An exemplary configuration of the screen 19 of FIG. 3 is
shown in FIG. 4. The screen 19 is constructed, for example, from
wires 21 between which there are situated openings 26 through which
a reducing agent flow 20 can pass. On one side, the wires 21 of the
screen 19 have flow-impeding devices 22 provided thereon which can
cover the openings 26 if the reducing agent flow 20 passes in the
opposite direction. The flow-impeding devices 22 act as valve
devices. A screen 19 of this type may, if appropriate, also be
combined with a filter ply 14. A screen 19 may then simultaneously
perform a supporting function for the filter ply 14 and define the
form and/or shape and position of the filter ply 14. The partition
layer 6 is then formed by a screen 19 with flow-impeding devices 22
in combination with a filter ply 14.
[0058] FIG. 5 illustrates a device 1 as seen from above in which
the tank 3 can also be seen. The chamber 9 in which the delivery
unit 4 is disposed is situated in the tank 3. The intake point 5,
through which a reducing agent can pass to the delivery unit 4, is
situated on the chamber 9. Reducing agent is drawn-in by the
delivery unit 4 by using the pump 17. The partition layer 6 is
situated around the chamber 9 and the delivery unit 4 in such a way
that an annular intermediate space 7 is formed around the chamber 9
and covers the intake point 5. Various guide structures 10, which
are disposed around the partition layer 6, divert the reducing
agent toward the partition layer 6 when the tank 3 or the device 1
is in an oblique position or in the event of sloshing movements in
the tank 3. An inflow direction 23 and an outflow direction 24
through the partition layer are defined. In FIG. 5, the partition
layer 6 is implemented, for example, with a filter ply 14 and with
a barrier ply 8.
[0059] FIG. 6 shows a motor vehicle 12 having an internal
combustion engine 13 and having an exhaust-gas treatment device 2
for the purification of the exhaust gases of the internal
combustion engine 13. The exhaust gas from the internal combustion
engine 13 flows through the exhaust gas treatment device 2 in an
exhaust gas flow direction 27. Reducing agent can be supplied into
the exhaust-gas treatment device 2 through an injector 28 by using
a device 1 for providing liquid reducing agent. For this purpose,
the device 1 has a tank 3, in which the reducing agent is stored,
and a delivery unit 4 which delivers the reducing agent from the
tank 3 to the injector 28. The device 1 may be constructed
correspondingly to the description given further above. An SCR
catalytic converter 29, in which the SCR process is performed, is
disposed in the exhaust-gas treatment device 2. Nitrogen oxide
compounds in the exhaust gas are converted with the aid of the
reducing agent. In order to operate the device 1, the motor vehicle
12 also has a control unit or controller 30 which is constructed to
control the operation of the device 1.
[0060] FIG. 7 shows a further embodiment of a device 1, having a
tank 3 and a delivery unit 4 which is disposed in a chamber 9 on
the tank bottom 25. The delivery unit 4 extracts the reducing agent
from the tank 3 at an intake point 5. The delivery unit 4 has a
pump 17 which serves for pumping the liquid additive. The delivery
unit 4 makes the liquid additive available at a line connector 16.
The intake point 5 is covered by a partition layer 6, in such a way
that a closed intermediate space 7 is formed. The partition layer 6
is formed in the manner of a cylinder and is disposed (in circular
fashion) around the chamber 9. The surface of the cylinder forms
the surface of the partition layer 6. The partition layer 6 has a
support structure 11 which may be formed in the manner of a screen.
The area of the partition layer 6 is divided into a first zone 31
and a second zone 32. The partition layer 6 is formed at least
partially from a first material 33 in the first zone 31. The
partition layer 6 is formed at least partially from a second
material 34 in the second zone 32. The first material 33 exhibits
improved or greater permeability to air in relation or compared to
the second material 34. The second material 34 preferably has
improved or greater permeability to reducing agent in an inflow
direction 23 than in an outflow direction 24.
[0061] It is clear that a person skilled in the art may readily
combine the content of the disclosure of the figures and associated
explanations, in such a way that details of one embodiment may be
used together with details of another embodiment. The only
exceptions to this are where explicitly stated above.
[0062] A particularly inexpensive device for the reliable provision
of liquid reducing agent for an exhaust-gas treatment device has
thus been proposed.
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