U.S. patent application number 12/444204 was filed with the patent office on 2010-01-14 for tank for storing a reducing agent.
Invention is credited to Rainer Haeberer, Matthias Horn.
Application Number | 20100006568 12/444204 |
Document ID | / |
Family ID | 38669415 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100006568 |
Kind Code |
A1 |
Haeberer; Rainer ; et
al. |
January 14, 2010 |
TANK FOR STORING A REDUCING AGENT
Abstract
The invention relates to a tank for storing a reducing agent, in
particular a liquid reducing agent for reducing nitrogen oxides
from the waste gas of an internal combustion engine to nitrogen and
water. The tank includes an external container in which an internal
container is accommodated. The internal container is held in the
external container in a mounting that can be axially displaced in
relation to an axis of the external container. The internal
container is held such that the volume in the external container is
modified by displacing the internal container in the mounting.
Inventors: |
Haeberer; Rainer; (Bretten,
DE) ; Horn; Matthias; (Freiberg, DE) |
Correspondence
Address: |
RONALD E. GREIGG;GREIGG & GREIGG P.L.L.C.
1423 POWHATAN STREET, UNIT ONE
ALEXANDRIA
VA
22314
US
|
Family ID: |
38669415 |
Appl. No.: |
12/444204 |
Filed: |
August 13, 2007 |
PCT Filed: |
August 13, 2007 |
PCT NO: |
PCT/EP2007/058344 |
371 Date: |
April 3, 2009 |
Current U.S.
Class: |
220/8 |
Current CPC
Class: |
Y02T 10/12 20130101;
F01N 2610/1406 20130101; B60K 15/03 20130101; F01N 3/2066 20130101;
Y02A 50/2325 20180101; Y02A 50/20 20180101; Y02T 10/24 20130101;
F01N 2610/02 20130101; B60K 13/04 20130101; F01N 2610/10 20130101;
B60K 2015/03348 20130101 |
Class at
Publication: |
220/8 |
International
Class: |
B65D 6/16 20060101
B65D006/16; F01N 3/00 20060101 F01N003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 4, 2006 |
DE |
10 2006 046 901.1 |
Claims
1-10. (canceled)
11. A tank for storing a reducing agent, in particular a liquid
reducing agent for reducing nitrogen oxides in the exhaust of an
internal combustion engine to nitrogen and water, comprising: an
outer container; an inner container accommodated within the inner
container; a mount supporting the inner container within the outer
container, wherein the mount is able to slide axially in relation
to an axis of the outer container, and the inner container is
supported so that a sliding of the inner container in the mount
changes the volume of the outer container.
12. The tank as recited in claim 11, wherein a spring element is
disposed between the inner container and the outer container.
13. The tail as recited in claim 12, wherein the spring element
rests with one end against a bottom of the inner container and
rests with an other end against a bottom of the outer
container.
14. The tank as recited in claim 12, wherein the spring element is
manufactured out of an elastomer.
15. The tank as recited in claim 13, wherein the spring element is
manufactured out of an elastomer.
16. The tank as recited in claim 11, wherein the inner container is
accommodated in an opening of the outer container in such a way
that the inner container protrudes from the outer container.
17. The tank as recited in claim 12, wherein the inner container is
accommodated in an opening of the outer container in such a way
that the inner container protrudes from the outer container.
18. The tank as recited in claim 13, wherein the inner container is
accommodated in an opening of the outer container in such a way
that the inner container protrudes from the outer container.
19. The tank as recited in claim 14, wherein the inner container is
accommodated in an opening of the outer container in such a way
that the inner container protrudes from the outer container.
20. The tank as recited in claim 15, wherein the inner container is
accommodated in an opening of the outer container in such a way
that the inner container protrudes from the outer container.
21. The tank as recited in claim 11, wherein the inner container is
embodied with a shoulder that is acted on by a coupling element,
which coupling element is attached to the outer container with
either frictional, nonpositive engagement or form-locked
engagement.
22. The tank as recited in claim 12, wherein the inner container is
embodied with a shoulder that is acted on by a coupling element,
which coupling element is attached to the outer container with
either frictional, nonpositive engagement or form-locked
engagement.
23. The tank as recited in claim 15, wherein the inner container is
embodied with a shoulder that is acted on by a coupling element,
which coupling element is attached to the outer container with
either frictional, nonpositive engagement or form-locked
engagement.
24. The tank as recited in claim 11 wherein an elastic sealing
element is accommodated between the inner container and the outer
container, in a region of the mount at which the inner container
protrudes from the outer container.
25. The tank as recited in claim 20, wherein an elastic sealing
element is accommodated between the inner container and the outer
containers in a region of the mount at which the inner container
protrudes from the outer container.
26. The tank as recited in claim 11, wherein the inner container is
connected to a supply module.
27. The tank as recited in claim 25, wherein the inner container is
connected to a supply module.
28. The tank as recited in claim 26, wherein the supply module is
connected to the inner container so as to be positioned outside of
the outer container.
29. The tank as recited in claim 27, wherein the supply module is
connected to the inner container so as to be positioned outside of
the outer container.
30. The tank as recited in claim 11, wherein a heating element is
accommodated in the inner container.
Description
PRIOR ART
[0001] The invention relates to a tank for storing a liquid
reducing agent according to the preamble to claim 1.
[0002] In internal combustion engines, particularly in
diesel-operated internal combustion engines, due to stricter
exhaust legislation going into effect in the next few years, it
will be necessary among other things to reduce the percentage of
nitrogen oxides in exhaust. In order to reduce the percentage of
nitrogen oxides, a selective catalytic reduction, for example, is
carried out in which the nitrogen oxides are reduced to nitrogen
and water with the aid of reducing agents. For example, an aqueous
urea solution is used as a reducing agent.
[0003] The reducing agent is normally stored in a tank and supplied
via a line from the tank to a metering module that injects the
reducing agent into the exhaust pipe, for example.
[0004] Depending on the antifreeze used, the conventional liquid
reducing agents currently in use freeze at a temperature in the
range from -11.degree. C. to -40.degree. C. The phase shift from
the liquid aggregate state into the solid aggregate state causes
the reducing agent to undergo a volume expansion of approximately
7%. In order to prevent the tank from bursting due to the freezing
of the reducing agent, in the tanks currently in use for storing
reducing agent, the tank is not completely filled so that if
freezing occurs, there is always an air cushion above the reducing
agent.
[0005] The presence of this air cushion produces a thermal
insulation of the reducing agent at the top of the tank. The
freezing of the reducing agent consequently begins at the sides and
the bottom. The volume expansion of the freezing liquid
consequently always occurs in the direction toward the air space in
the tank, toward the middle of the tank. As a result, the reducing
agent causes a dome to form as it freezes. The presence of the air
cushion prevents the tank from being damaged when the reducing
agent freezes.
[0006] A disadvantage of the air cushion in the tank, however, is
that if the tank is overfilled, an expansion of the reducing agent
can cause damage to the tank.
DISCLOSURE OF THE INVENTION
Advantages of the Invention
[0007] A tank embodied according to the invention for storing a
reducing agent, in particular a liquid reducing agent for reducing
nitrogen oxides in the exhaust of an internal combustion engine to
nitrogen and water, includes an outer container in which an inner
container is accommodated. The inner container is accommodated in
the outer container in a mount that is able to slide in relation to
an axis of the outer container, the inner container being supported
so that a sliding of the inner container in the mount changes the
volume of the outer container.
[0008] An advantage of the tank according to the invention is that
a deformation of the outer container during the freezing of the
reducing agent leads to a shifting of the wall of the outer
container without a shifting of the inner container, enlarging the
volume in the outer container. The fixed positioning of the inner
container avoids damage that can occur if the position of the inner
container changes. Such damage can include, for example, the
bending or rupturing of fixed connections or rigid lines with which
the inner container is attached, for example, to a vehicle
body.
[0009] In one embodiment, a spring element is accommodated between
the inner container and the outer container. The spring element
permits the inner container to be axially fixed in relation to the
outer container. Through the use of a spring element, however, it
remains possible for the inner container to slide in an axial
direction in the outer container. The spring element preferably
rests with one end against the bottom of the inner container and
rests with the other end against the bottom of the outer container.
The spring element, which is accommodated between the inner
container and the outer container, is preferably manufactured out
of elastomer.
[0010] In order for the volume of the outer container to increase
due to the sliding of the inner container, it is preferable for the
inner container to be accommodated in an opening in the outer
container in such a way that the inner container protrudes from the
outer container. If the inner container were completely enclosed by
the outer container, then a sliding of the inner container would
only result in a geometrical change of the volume of the outer
container, but the volume would remain the same size.
[0011] In order to attach the inner container to the outer
container, the inner container is preferably embodied with a
shoulder that is acted on by a coupling element, which is attached
to the outer container with either frictional, nonpositive
engagement or form-locked engagement. A suitable coupling element,
for example, is a coupling nut that is screwed onto a thread
encompassing the inner container.
[0012] In order to permit the inner container to slide axially when
it is fastened to the outer container with the aid of the coupling
element, preferably an elastic sealing ring is accommodated between
the inner container and the outer container, in the region of the
axial mount at which the inner container protrudes from the outer
container. In this instance, the elastic sealing ring rests, for
example, on the shoulder of the inner container while the outer
container rests against the opposite side of the elastic sealing
ring. As soon as the reducing agent freezes and the volume of the
reducing agent increases as a result, the wall of the outer
container is moved upward along the inner container due to the
volume increase of the reducing agent while the coupling element
lifts up from the sealing ring. The elastic sealing ring in this
case preferably expands in order to assure the tightness of the
seal. Another purpose of the elastic sealing ring is to provide a
seal that protects the connection between the outer container and
the inner container from the surrounding environment so that no
reducing agent can escape from the outer container. This is
particularly necessary when the reducing agent in the outer
container is not frozen.
[0013] The inner container is preferably connected to a supply
module. The connection of the supply module to the inner container
is preferably embodied so as to prevent a relative movement between
the supply module and the inner container. To this end, the supply
module is preferably placed directly onto the inner container. The
supply module generally includes a pump with which reducing agent
can be drawn from the inner container.
[0014] The inner container preferably also accommodates a heating
element that can be used to thaw frozen reducing agent. The heating
element is preferably also connected to the supply module and is
triggered by means of the supply module. Attaching the supply
module to the inner container so as to prevent a relative movement
between the inner container and the supply module also prevents
damage to the heating element that would occur if the supply module
were to move in relation to the inner container as soon as the
reducing agent in the inner container froze solid. The relative
movement between the supply module and inner container would occur,
for example, because the freezing of the reducing agent would push
against the supply module and lift it from the inner container if a
sufficient attachment were not provided. Since the heating element
is generally rigidly connected to the supply module and is no
longer mobile due to the frozen reducing agent in the inner
container, this might possibly cause the heating element to be torn
out from the supply module. A heating would no longer be possible,
thus rendering it no longer possible to thaw the reducing agent. In
general, the tank is constructed so that the supply module
connected to the inner container is positioned outside the outer
container. The positioning of the supply module outside the outer
container makes it possible, for example in the event of damage to
the supply module, to simply repair and replace the supply module
without having to disassemble the entire tank.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Exemplary embodiments of the invention are shown in the
drawings and explained in greater detail in the following
description.
[0016] Drawings
[0017] FIG. 1 shows a tank for storing reducing agent in which the
reducing agent is frozen,
[0018] FIG. 2 is a schematic depiction of a tank embodied according
to the invention for storing a reducing agent,
[0019] FIG. 3 is a detailed depiction of an attachment of an inner
container in an outer container with a coupling element.
EMBODIMENTS OF THE INVENTION
[0020] FIG. 1 shows a tank for storing a reducing agent. A tank 1
includes an outer container 3 in which an inner container 5 is
accommodated. The inner container 5 is fastened to the outer
container 3, for example by means of a coupling element. A suitable
coupling element is a coupling nut, for example. It is also
conceivable, however to use any other fastening option known to
those skilled in the art. The inner container 5 is attached to a
supply module 7. For example, the supply module 7 includes a supply
pump with which reducing agent can be supplied from the inner
container 5. The supply module 7 is also connected to a heating
element 9. The heating element 9 can be used to thaw the reducing
agent in the inner container 5 when it is frozen. The heating
element is preferably embodied so that it encompasses a supply line
11. The fact that the supply line 11 is encompassed by the heating
element 9 means that frozen reducing agent that is contained in the
supply line 11 is thawed first. The supply line 11 is connected to
the supply pump 13 contained in the supply module 7. The supply
pump 13 is connected to a reducing agent line 15. The reducing
agent line 15 ends at a metering device 17 that supplies the liquid
reducing agent to an SCR (selective catalytic reduction) catalytic
converter, which is not depicted here. Nitrogen oxides, which are
produced during the combustion of fuel in an internal combustion
engine and are conveyed out with the exhaust, are reduced to
nitrogen and water in the SCR catalytic converter. The reducing
agent, for example, is an aqueous urea solution.
[0021] In the hot exhaust, the liquid reducing agent evaporates and
forms ammonia that is deposited in the SCR catalytic converter. The
nitrogen oxides contained in the exhaust are converted into
elementary nitrogen and water vapor by the ammonia that is
deposited in the SCR catalytic converter.
[0022] At temperatures below its melting point, the liquid reducing
agent freezes. The freezing process begins at the walls of the
outer container 3 and continues on into the interior of the outer
container 3. When an aqueous urea solution is used as a liquid
reducing agent, it freezes at a temperature between -11.degree. C.
and -40.degree. C. The temperature depends on which antifreeze or
how much antifreeze has been added to the liquid reducing agent. It
generally takes several days for the reducing agent to freeze
completely. The volume expansion of the reducing agent as it
freezes causes a dome 19 to form. Since the freezing process begins
at the walls of the outer container 3 and continues on into the
interior, the dome 19 encompasses the inner container 5. The frozen
reducing agent in the outer container is labeled with the reference
numeral 21 in FIG. 1.
[0023] So that the formation of the dome 19 does not destroy the
outer container 3, the outer container 3 is only filled to a level
that leaves an air space 23 above the reducing agent. The formation
of the dome 19 displaces air from the air space 23. The size of the
air space 23 is selected to be large enough to avoid a deformation
of the outer container 3, even when the reducing agent 21 is
completely frozen. The volume taken up by the air space 23 is at
least equal to the volume by which the reducing agent expands when
it freezes.
[0024] After the reducing agent in the outer container 3 has frozen
to the point that the frozen reducing agent 21 contacts the wall 25
of the inner container 5, the reducing agent in the inner container
5 also begins to freeze. In the inner container 5 as well, the
freezing process begins at the wall 25 and continues on toward the
middle of the inner container 5. In the embodiment show in FIG. 1,
a part of the reducing agent inside the inner container 5 is
already frozen. This frozen reducing agent in the inner container
is labeled with the reference numeral 27. Since the reducing agent
is not yet completely frozen, the inner container 5 also contains
liquid reducing agent 29. Since the freezing process begins at the
walls 25 of the inner container 5, the frozen reducing agent 27
encompasses the liquid reducing agent 29. When the liquid reducing
agent 29 in the inner container 5 freezes further, the phase
boundary 31 between the frozen reducing agent 27 and the liquid
reducing agent 29 moves further upward and toward the center. The
volume expansion of the reducing agent then causes a dome to also
form in the inner container 5. For this reason, it is likewise
necessary for the inner container 5 to contain an air cushion 33 in
order to avoid damage to the inner container. So that the freezing
of the reducing agent in the inner container 5 does not damage the
heating element 5, the inner container 5 is preferably rigidly
connected to the supply module 7.
[0025] The inner container 5 in this case is rigidly connected to
the outer container 3. It is not possible for the inner container 5
to move in the outer container 3. If the outer container is
overfilled and the air cushion 23 is too small, then the frozen
reducing agent pushes the wall of the outer container 3 outward.
This can damage the outer container 3.
[0026] FIG. 2 shows a tank embodied according to the invention,
with an axially sliding inner container.
[0027] A tank 1 embodied according to the invention likewise
includes an inner container 5 that is accommodated in an outer
container 3. The inner container 5 is connected to the supply
module 7 so as to form a functional unit. The connection of the
inner container 5 to the supply module 7 is known to those skilled
in the art and is therefore depicted only schematically here.
[0028] According to the invention, the inner container 5 is
accommodated in the outer container in an axial mount 35 that is
able to slide in relation to an axis 37 in the outer container 3.
As soon as the reducing agent in the outer container 3 freezes and
therefore expands, the inner container 5 that is attached to the
supply module 7 to form the functional unit is pushed out of the
inner container 3 in the axial direction. This avoids damage to the
outer container 3 when the reducing agent freezes, even if the
outer container 3 is overfilled, thus leaving an insufficient air
cushion.
[0029] Any mount known to those skilled in the art is suitable for
use as the axially movable mount 35. In order to prevent the inner
container 5 from starting to move inside the outer container 3,
e.g. due to externally exerted forces, the inner container 5 is
elastically attached to the outer container 3. The attachment of
the inner container 5 to the outer container 3 is carried out, for
example as shown in FIG. 2, by means of a spring element 39, which
is accommodated between the bottom 41 of the inner container 5 and
the bottom 43 of the outer container 3. In order to prevent the
inner container 5 from starting to oscillate, it is necessary for
the spring element 39 to have a sufficiently high spring constant.
A suitable spring element 39, for example, is a cushion composed of
an elastomer.
[0030] Movements of the inner container 5 in the outer container 3
are induced, for example, when the tank 1 embodied according to the
invention is used in a motor vehicle. As soon as the motor vehicle
is driven, irregularities in the road surface are transmitted to
the motor vehicle and therefore also to the tank 1. Because of the
differing masses of the outer container 3 and inner container 5,
these are accelerated differently so that the movements of the
vehicle cause a relative movement between the outer container 3 and
the inner container 5. The spring element 39 reduces or preferably
completely eliminates this relative movement between the inner
container 5 and the outer container 3.
[0031] The axially movable mount 35 is preferably embodied so that
it is fluid-tight. This prevents liquid reducing agent from being
able to escape from the outer container 3 into the environment.
[0032] FIG. 3 shows an example of an axially movable mount.
[0033] In the embodiment shown in FIG. 3, the functional unit 45
including the inner container 5 and the supply module 7 is fastened
to the outer container 3 with a coupling element 47. To this end,
the outer container 3 is provided with a sleeve-shaped extension 49
on which an external thread 51 is embodied. The sleeve-shaped
extension 49 encompasses an opening 54 into which the functional
unit 45 is inserted. In order to secure the functional unit 45 in
the outer container 3, a shoulder 53 is embodied on the functional
unit 45. The coupling element 47, which in this case is embodied in
the form of a coupling nut and is screwed onto the external thread
51 on the sleeve-shaped extension 49, acts on the shoulder 53 and
secures the functional unit 45 in the outer container 3. In order
to produce a seal, an elastic sealing element 55 is accommodated
between the sleeve-shaped extension 49 and the functional unit 45.
Preferably, the sealing element 55 is profiled. Because of the
profiling, the sealing element 55 is radially elastic. The sealing
element 55 is mounted between the sleeve-shaped extension 49 and
the functional unit 45 with a moderate amount of radial
prestressing. On the one hand, this permits the functional unit 45
to slide axially in the outer container 3 in relation to the axis
37 and on the other hand, this also provides a seal between the
functional unit 45 and the outer container 3 so that no reducing
agent can escape from the outer container 3 into the
environment.
[0034] In a preferred embodiment, the sealing element 55 has a
collar 57 that rests against the shoulder 53, thus assuring an
additional axial seal. To permit an axial sliding of the functional
unit 45 in the outer container 3, though, it is necessary for the
collar 57 to be very elastic. This can be assured, for example, by
means of an intense profiling. Another purpose of the collar 57 is
to axially position the sealing element 55 in the axially movable
mount 35 that is composed of the sleeve-shaped extension 49 and the
functional unit 45 accommodated therein. A sufficiently large
distance between the shoulder 53 and the coupling element 47 is
achieved by the fact that the coupling element 47 is placed against
a stop 59. The stop 59 is embodied, for example, as an end surface
on the sleeve-shaped extension 49.
[0035] The spring element 39, which in the embodiment shown here is
embodied as an elastomer part, prevents the functional unit 45 from
falling into the outer container 3 until it rests against the
bottom of the outer container 3. The spring element 39 establishes
a distance between the bottom 41 of the inner container 5 and the
bottom 43 of the outer container 3. The height of the spring
element 39 also establishes the distance between the shoulder 53
and the coupling element 47.
[0036] If the reducing agent in the outer container 3 then begins
to freeze, a force is exerted on the outer container 3. This is
depicted by the arrows 61. The force 61 acting on the outer
container 3 causes the casing of the outer container 3 to be pushed
outward. This upward-directed deformation can be absorbed by the
axially movable mount 35, thus preventing a damage to the tank 1.
Even when a deformation of the casing of the outer container 3
occurs, the functional unit 45 remains in its position. As a result
no strain is exerted on lines and devices connecting the functional
unit 45 to a vehicle body, for example. It is also not a problem if
the coupling element 47 lifts away from the collar 57 of the
sealing element 55 because it is not necessary for a seal to
prevent the escape of liquid if the reducing agent in the outer
container 3 is frozen. As soon as the reducing agent has thawed
again, the coupling element 47 drops back down onto the collar 57
and the collar 57 produces the axial seal once more. The spring
element 39 can also hold the functional unit 45 in its position if
the bottom 43 of the outer container 3 moves in relation to the
functional unit 45. With a rigid connection of the functional unit
45 to the bottom 43 of the outer container 3, the functional unit
45 would move in relation to the vehicle body and this could result
in damage.
* * * * *