U.S. patent application number 14/518096 was filed with the patent office on 2015-02-05 for method for draining a delivery unit for liquid additive, delivery unit and motor vehicle having a delivery unit.
The applicant listed for this patent is EMITEC GESELLSCHAFT FUER EMISSIONSTECHNOLOGIE MBH. Invention is credited to JAN HODGSON, CARSTEN KRUSE, THOMAS NAGEL, SVEN SCHEPERS.
Application Number | 20150033712 14/518096 |
Document ID | / |
Family ID | 48128307 |
Filed Date | 2015-02-05 |
United States Patent
Application |
20150033712 |
Kind Code |
A1 |
KRUSE; CARSTEN ; et
al. |
February 5, 2015 |
METHOD FOR DRAINING A DELIVERY UNIT FOR LIQUID ADDITIVE, DELIVERY
UNIT AND MOTOR VEHICLE HAVING A DELIVERY UNIT
Abstract
A method for draining a delivery unit for a liquid additive, in
particular a urea-water solution, includes at least: a) producing
an electrical connection by using a currentless switch which is
constructed to produce an electrical connection when a temperature
falls below a threshold temperature; and b) draining the delivery
unit when, in step a), the electrical connection has been produced.
The method can be used, in particular, in SCR systems for
exhaust-gas aftertreatment for motor vehicles. A delivery unit and
a motor vehicle having a delivery unit are also provided.
Inventors: |
KRUSE; CARSTEN; (TROISDORF,
DE) ; NAGEL; THOMAS; (ENGELSKIRCHEN, DE) ;
SCHEPERS; SVEN; (TROISDORF, DE) ; HODGSON; JAN;
(TROISDORF, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EMITEC GESELLSCHAFT FUER EMISSIONSTECHNOLOGIE MBH |
LOHMAR |
|
DE |
|
|
Family ID: |
48128307 |
Appl. No.: |
14/518096 |
Filed: |
October 20, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2013/057896 |
Apr 16, 2013 |
|
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|
14518096 |
|
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Current U.S.
Class: |
60/285 ; 137/2;
137/59 |
Current CPC
Class: |
Y10T 137/0324 20150401;
H01H 37/52 20130101; Y02T 10/12 20130101; Y02T 10/24 20130101; H01H
37/46 20130101; Y02A 50/20 20180101; Y02A 50/2325 20180101; Y10T
137/1189 20150401; F01N 3/005 20130101; F01N 3/2066 20130101; H01H
37/36 20130101; F01N 2610/01 20130101; F01N 3/206 20130101; F01N
2610/1486 20130101 |
Class at
Publication: |
60/285 ; 137/2;
137/59 |
International
Class: |
F01N 3/00 20060101
F01N003/00; F01N 3/20 20060101 F01N003/20 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 19, 2012 |
DE |
102012103453.2 |
Claims
1. A method for draining a delivery unit for liquid additive, the
method comprising the following steps: a) producing an electrical
connection using a currentless switch constructed to produce an
electrical connection when a temperature falls below a threshold
temperature; and b) draining the delivery unit when, in step a),
the electrical connection has been produced.
2. The method according to claim 1, which further comprises
activating a control unit by using the switch in step a), and
controlling the draining in step b) by using the control unit.
3. The method according to claim 2, which further comprises
automatically deactivating the control unit after execution of the
method.
4. The method according to claim 1, which further comprises:
performing a temperature measurement between step a) and step b) by
using a temperature sensor in order to check if a threshold
temperature has actually been undershot; and removing the liquid
additive from the delivery unit in step b) only if the threshold
temperature has actually been undershot.
5. The method according to claim 1, which further comprises:
storing the drainage of the delivery unit in a memory after step
b); at least one of before step a) or after step a), checking if
the delivery unit has already been drained based on information in
the memory; and at least carrying out step b) only when the
delivery unit has not been drained.
6. The method according to claim 1, which further comprises
carrying out the step of draining the delivery unit by back-suction
of the liquid additive into a tank.
7. The method according to claim 1, which further comprises
selecting the switch at least from the following group: a bimetal
switch, a switch including a shape memory alloy, a temperature
switch with a liquid, and a prestressed switch.
8. The method according to claim 1, which further comprises
executing the method during a standstill phase of an internal
combustion engine.
9. A delivery unit for delivering a liquid additive, the delivery
unit comprising: a tank; a delivery line connected to said tank; a
pump configured to deliver liquid additive through said delivery
line from said tank; and a currentlessly activatable switch
connected to said pump and configured to produce an electrical
connection when a threshold temperature is undershot.
10. A motor vehicle, comprising: an internal combustion engine; an
exhaust-gas treatment device configured to purify exhaust gases of
said internal combustion engine; and a delivery unit according to
claim 9 associated with 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/EP2013/057896, filed
Apr. 16, 2013, which designated the United States; this application
also claims the priority, under 35 U.S.C. .sctn.119, of German
Patent Application DE 10 2012 103 453.2, filed Apr. 19, 2012; 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 method for draining a delivery
unit for liquid additive. The invention also relates to a delivery
unit and a motor vehicle having a delivery unit.
[0003] Such delivery units are used, for example, for delivering
urea-water solution as liquid additive into the exhaust-gas
treatment device of an internal combustion engine. Urea-water
solution is used in exhaust-gas treatment devices for the removal
of nitrogen oxide compounds from the exhaust gases within the
context of the SCR process [SCR=selective catalytic reduction]. A
32.5% urea-water solution which is available under the trademark
AdBlue.RTM. is typically used.
[0004] A problem with such delivery units is the fact that the
liquid additives can freeze during long standstill periods of the
delivery units. The described urea-water solution, for example,
freezes at -11.degree. C. Such low temperatures may arise, in
particular, during long standstill phases of a motor vehicle in
winter.
[0005] Water-based liquid additives, in particular, (such as the
urea-water solution) expand in terms of their volume as they
freeze. That can damage the delivery unit. It is therefore known
from the prior art to drain a delivery unit upon the cessation of
operation of a motor vehicle. The liquid additive which is located
in the delivery unit is usually delivered back, during the draining
process, into a tank in which the liquid additive is stored.
[0006] It is a problem in that case that the draining of the
delivery unit typically leads to a cumbersome configuration of the
system and/or to increased consumption of the additive. Increased
consumption occurs, for example, because the liquid additive
located in the delivery unit cannot be completely recovered when
draining occurs. Under certain circumstances, a residual quantity
of the liquid additive remains in the delivery line. That residual
quantity can evaporate there. As a result of the draining, it is
also necessary to refill the delivery unit when re-activation
occurs. During that refilling it is also possible for a loss of
liquid additive to occur, for example because when refilling occurs
an excess of liquid additive occurs and the excess escapes from a
feed device of the delivery unit.
[0007] Under certain circumstances, delivery unit wear which occurs
as a result of the draining process is also problematic. In
particular, a pump of the delivery unit can be subject to increased
wear as a result of the draining process.
SUMMARY OF THE INVENTION
[0008] It is accordingly an object of the invention to provide a
method for draining a delivery unit for liquid additive, a delivery
unit and a motor vehicle having a delivery unit, which overcome the
hereinafore-mentioned disadvantages and solve or at least alleviate
the highlighted technical problems of the heretofore-known methods,
units and vehicles of this general type. It is sought, in
particular, to disclose an especially suitable method for draining
a delivery unit. It is likewise sought to specify a delivery unit
for realizing the method which is simply constructed and, if
appropriate, can also be retrofitted. In particular, the method
and/or the delivery unit should be suitable for use in SCR
exhaust-gas aftertreatment systems in the automotive field.
[0009] With the foregoing and other objects in view there is
provided, in accordance with the invention, a method for draining a
delivery unit for liquid additive, comprising at least the
following steps: [0010] a) producing an electrical connection by
using a currentless switch which is constructed to produce an
electrical connection when a temperature falls below a threshold
temperature; and [0011] b) draining the delivery unit when, in step
a), the electrical connection has been produced.
[0012] The delivery unit that can be drained by using the described
method preferably has at least one delivery line which extends from
a tank for the liquid additive to a feed device (nozzle, injector,
valve or the like) for the feed of the liquid additive to a
consumer (for example an exhaust-gas treatment device). The
delivery line is connected to the tank at an extraction point so
that liquid additive from the tank can enter the delivery line. A
pump, which is preferably disposed in the delivery line, pumps the
liquid additive through the delivery line. The delivery line and
the pump are filled with liquid additive during the delivery
operation of the delivery unit. The delivery unit may have further
components filled with liquid additive.
[0013] The method is implemented specifically when the delivery
unit and/or the motor vehicle are/is deactivated, that is to say,
for example, no ignition is applied or the engine is inactive. The
method may thus be activated, for example, when the motor vehicle
is deactivated.
[0014] The switch used in step a) is preferably distinguished in
that the operation thereof does not require any current before the
electrical connection has been produced. It is preferable if, in
the switch, a mechanical and/or physical effect is utilized which
produces the electrical connection. The thermal expansion of a
material or phase changes of a material may be specified as
examples for correspondingly utilizable mechanical and/or physical
effects. The switch is thus in a currentless standby position
before step a). The switch is referred to in step a) as a
currentless switch. This also means, in particular, that the switch
is not actuated by an electrical connection. There is, in
particular, no electrical actuation line through which an
electrical signal can arrive at the switch in order to control the
position of the switch.
[0015] The switch is preferably configured in such a way that it
produces the electrical connection when a temperature in the
surroundings of the switch reaches or drops below a (lower)
threshold temperature. This threshold temperature is typically
above a freezing temperature of the liquid additive being used. The
threshold temperature is determined by the structure of the
switch.
[0016] Basically, the switch can interact with the delivery unit
and/or is part of the delivery unit itself. If the delivery unit is
integrated into a motor vehicle, the switch can, where appropriate,
then also be provided at a position which is disposed remotely from
the delivery unit. The position of the switch should be selected,
in particular, in such a way that with the switch it is possible to
acquire or predict information which is characteristic of the
current aggregate state of the additive. For this purpose, the
delivery unit has, in particular, a detection device with which the
current state of the switch can be detected, in particular it can
be detected whether the latter is currentless or energized. Of
course, it may also be appropriate to provide a plurality of such
switches which can then make available information on the ambient
temperature and/or the aggregate state of the additive for, for
example, different sections of the delivery unit. The information
which is acquired with a plurality of switches can be used to
define when partial/complete draining is to be initiated or carried
out.
[0017] At least a (significant) part of the liquid additive, but
preferably all of the liquid additive, is transported (in
particular in the pump and/or the delivery line) out of the
delivery unit components which are filled with liquid additive,
during the draining process in step b). It is expedient for such an
amount of liquid additive to be transported out that the residual
amount of liquid additive that may remain in the delivery unit
cannot lead to damage to the delivery unit if the liquid additive
freezes.
[0018] Due to the described method, it is not necessary to perform
a draining during every operational stoppage of the delivery unit
or of the motor vehicle. It is rather also possible for a draining
to be performed as required when there is a threat of freezing of
the liquid additive due to low outside temperatures. For example,
urea-water solution with a 32.5 percent urea content freezes at
-11.degree. C. It is therefore advantageous if the threshold
temperature of the switch is set, for example, in the range from
-7.degree. C. to -10.degree. C. in order to drain the delivery unit
when there is a threat of freezing of the liquid additive.
[0019] No permanent current supply (of the dedicated and/or
superordinate controller) is required for the described method
while the motor vehicle is at a standstill. Due to the described
method, there is no (significant) current consumption for as long
as draining is not being performed. The switch is therefore used to
"wake" the components required for the draining only when the
predefined threshold temperature is attained outside or in a
temperature-sensitive region of the delivery unit.
[0020] As a result of the described method it becomes possible in
particular, also to avoid the sucking of impurities into the
delivery line of the delivery unit. During the draining, the liquid
additive is preferably delivered back into the tank from the
delivery unit counter to the delivery direction. Within the
process, the liquid additive is replaced by gas or by air. The gas
or the air is preferably sucked in by a supply device during the
draining process. If the supply device is disposed at an
exhaust-gas treatment device, under certain circumstances
impurities from the exhaust gas are also sucked into the delivery
unit. As a result of the fact that the draining is not carried out
whenever a motor vehicle is deactivated but rather only when the
present temperature actually requires it, the risk of contamination
of the delivery line by impurities from the exhaust gas can be
considerably reduced.
[0021] In accordance with another particularly preferred mode of
the method of the invention, a control unit is activated by using
the switch in step a), and the control unit controls the draining
in step b).
[0022] It is preferable if a control unit is activated by using the
switch in step a) and the control unit controls the draining
process. In order to carry out the draining process it is, for
example, the case that a pump is activated for the draining. It may
additionally be expedient for valves to be opened, through which
the draining then takes place. In order to coordinate the actuation
of the pump and if appropriate the actuation of valves, it is
advantageous for a control unit to be used which performs the
coordination. The control unit can, for example, also be the engine
control unit of a motor vehicle which is activated or woken up by
step a).
[0023] In accordance with a further advantageous mode of the method
of the invention, the control unit automatically deactivates after
the execution of the method.
[0024] The current consumption of the method can be further reduced
by using an automatic deactivation of the control unit after the
execution of step b). For the purpose of deactivation, for example
a deactivation switch is present which, like the currentless
switch, is configured to interrupt the electrical connection. In
contrast to the currentless switch, the deactivation switch is not
actuated in a currentless fashion as a function of the temperature
but instead can be actuated by the control unit itself through a
signal line. The deactivation switch is actuated only if the
delivery line is already drained (to the desired extent). If the
deactivation switch has been activated, it is no longer possible to
activate the control unit by using the currentless switch. The
deactivation switch can also be integrated in the control unit. In
other words, the control unit can have an (internal) shut-down
device which deactivates the control unit independently of the
position of the currentless switch.
[0025] In accordance with an added advantageous mode of the method
of the invention, between step a) and step b), a temperature
measurement is performed by using a temperature sensor in order to
check whether or not a threshold temperature has actually been
undershot, and the liquid additive is removed from the delivery
unit in step b) only if the threshold temperature has actually been
undershot.
[0026] In order to avoid a fault as a result of an erroneous
tripping of the currentless switch in step a), it is advantageous
if, before the initiation of step b), the control unit additionally
performs a check of the temperature by using (at least) an
(additional and/or electrical) temperature sensor, in order to
ensure that the delivery unit is drained only if the threshold
temperature has actually been undershot. The (sensor-measured)
threshold temperature may deviate from the threshold temperature
for the activation of the currentless switch in step a), in order,
if appropriate, to avoid an unnecessary draining of the delivery
unit in step b). For example, a threshold temperature of the switch
can be set in such a way that the control unit is already activated
at a temperature of -7.degree. C. If the temperature drops to
-10.degree. C., the actual draining (step b) can then be carried
out, with this then being triggered by a measurement result
determined at the temperature sensor. Due to such additional
checking of the temperature it is possible to detect particularly
reliably situations in which draining of the delivery line is
necessary. In particular it is also possible for the accuracy of
the limiting temperature of the currentless switch to be lower than
the accuracy of the temperature measurement with the additional
temperature sensor. For example, the threshold temperature can have
an uncertainty level of more than .+-.3.degree. C., while the
accuracy of the additional sensor is less than .+-.1.degree. C. As
a result of the additional checking, this inaccuracy of the
currentless switch can be at least partially compensated.
[0027] In accordance with an additional advantageous mode of the
method of the invention, after step b), it is stored in a memory
that the delivery unit has been drained, and before step a) and/or
after step a), it is checked on the basis of the information in the
memory whether or not the system has already been drained, and at
least step b) is carried out only when the system has not been
drained.
[0028] By virtue of the fact that the present state of the delivery
unit (drained or not drained) is stored in a memory, it is possible
to avoid situations in which the described method is executed
multiple times during a (single) stoppage of operation. It is
possible, in particular, to avoid a situation in which the delivery
unit is damaged by the attempt to re-drain the already drained
delivery unit. An (electronic) memory for checking whether step b)
is to be carried out can alternatively or additionally be taken
into account for the deactivation of the control unit with a
deactivation switch. The information as to whether draining was
carried out or not, stored in the memory, can, in particular also
be used during re-activation of the delivery unit in order, where
appropriate, to perform refilling of the delivery unit when the
delivery unit has been drained.
[0029] In accordance with yet another advantageous mode of the
method of the invention, the delivery unit is drained by
back-suction of the liquid additive back into a tank.
[0030] Back-suction counter to a normal delivery direction is a
particularly advantageous way of draining the delivery unit in step
b). The back-suction is made possible by using a (single) pump
which can be operated counter to the normal delivery direction. In
a further structural variant, it is also possible to provide a
return line which branches off from the delivery line, in such a
way that draining is performed by using delivery in a circuit. It
is also possible for a separate pump to be used for the
back-suction.
[0031] Draining preferably takes place counter to a (normal)
delivery direction of the delivery unit, wherein the (normal)
delivery direction extends from the tank to the supply device along
a delivery line. The delivery direction of the pump is reversed for
this purpose. Depending on the construction of the pump, this can
take place by reversing the drive direction of the pump or by
suitable switching of valves which are assigned to the pump.
[0032] In particular, during the back-suction, there is the risk of
air being sucked into the delivery unit through a feed device
(injector, etc.). The feed device is the same feed device used for
feeding the liquid additive to a consumer (for example an
exhaust-gas treatment device). It is also possible for an
additional valve to be provided through which air can be sucked
into the delivery unit during the draining.
[0033] A further possibility for the draining in step b) is for the
delivery unit to be (partially) blown empty by using air. For this
purpose, a compressed-air line may be utilized which is connected
to the delivery unit or to the line system.
[0034] In accordance with yet a further advantageous mode of the
method of the invention, the switch is at least a switch from the
following group: [0035] a bimetal switch, [0036] a switch including
a shape memory alloy, [0037] a temperature switch with a liquid,
and [0038] a prestressed switch.
[0039] In the case of a bimetal switch, two different materials
with different thermal coefficients of expansion are disposed
adjacent one another and connected to one another. The form/shape
of the bimetal configuration varies as a result of temperature
variations. For example, the configuration bends. The variation of
the form/shape may be utilized to mechanically close a contact. An
electrical connection can be closed in this way.
[0040] In the case of a shape memory alloy, the form of a component
varies due to a phase change, whereby the electrical connection can
be closed. A nickel-titanium alloy is mentioned herein as an
example of a shape memory alloy. Polymer materials which exhibit
shape memory characteristics may also be used for the switch.
[0041] A temperature switch with a liquid may, for example, have a
sleeve filled with liquid. If the liquid freezes, its volume
changes. The change in volume can be utilized to thereby close an
electrical connection.
[0042] A (mechanically) prestressed switch which is used for the
described method is preferably constructed in such a way that when
the threshold temperature is reached the switch experiences a
sudden change in shape which produces an electrical contact. Such a
switch can include, for example, a prestressed expansion material
(for example a mechanically prestressed metal) which up to the
threshold temperature is located in a first position and changes
into a second position when the threshold temperature is reached.
In this context, in the first position the expansion material is
preferably located in a prestressed (unstable) position and is
prestressed (for example against a stop). When the threshold
temperature is exceeded, the expansion material can no longer be
held in the first position and changes (suddenly) into a second
position. Where appropriate, an actuator with which the prestressed
switch can be actively moved back into the prestressed first
position can also be present.
[0043] In accordance with yet an added advantageous mode of the
method of the invention, the method is executed during a standstill
phase of an internal combustion engine. In this context it is also
particularly advantageous if the draining or the execution of step
b) is (actively) prevented during the operation of an internal
combustion engine.
[0044] During an operating phase of an internal combustion engine,
the delivery unit is usually required to feed the liquid additive
to the exhaust-gas treatment device of the internal combustion
engine in order to ensure effective exhaust gas purification. The
draining should therefore preferably not take place. It is
therefore advantageous if the non-electronic switch is bypassed
and/or blocked during operation of an internal combustion
engine.
[0045] With the objects of the invention in view, there is also
provided a delivery unit comprising a currentless switch such as is
used for step a) of the described method. The advantages and
structural features explained for the described method can be
transferred analogously to the described delivery unit. The
delivery unit preferably has a housing in which the pump, the
switch and at least one portion of the delivery line are situated.
In the housing there may additionally be provided a control unit or
controller which is configured or programmed to execute the
described method. The delivery unit with the switch constitutes a
component that can be installed in a motor vehicle (in particular a
tank).
[0046] With the objects of the invention in view, there is
concomitantly provided a motor vehicle which will be described by
way of example in the text which follows.
[0047] The motor vehicle is shut down at temperatures above the
freezing point of urea, wherein the freezing point of urea is the
freezing point of the liquid additive. The control unit is in a
rest state (ignition off). If the vehicle is shut down for a
relatively long period of time, it must be ensured that repeated
draining by suction (activation of pump and injector) does not take
place. Draining by suction can be performed only once between two
engine starting processes. The following measures may therefore be
implemented: [0048] a) by using a bimetal switch (or some other
mechanically tripped contact/switch) which switches a contact at
approximately -9.degree. C., the control unit is activated, and the
injector is opened and the system is drained by suction. The
information that draining by suction has taken place is stored and
is accessed upon a restart of the system, in such a way that the
system knows that draining by suction has taken place; [0049] b)
without the control unit, the pump and the injector are activated,
and the action is stored in a type of memory, in such a way that
the information can be accessed upon a start of the engine.
[0050] In this way, draining of the system as required is ensured,
and the back-suction takes place only when the exhaust system has
cooled down and thus also the risk of the ingestion of particles
has been minimized.
[0051] Other features which are considered as characteristic for
the invention are set forth in the appended claims, noting that the
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.
[0052] Although the invention is illustrated and described herein
as embodied in a method for draining a delivery unit for liquid
additive, a delivery unit and a motor vehicle, 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.
[0053] 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
[0054] FIG. 1 is a schematic and block diagram of a motor vehicle
having a delivery unit which is configured to carry out the method
described herein;
[0055] FIG. 2 is a diagrammatic, longitudinal-sectional view of a
first embodiment variant of a currentless switch;
[0056] FIG. 3 is a longitudinal-sectional view of a second
embodiment variant of a currentless switch; and
[0057] FIG. 4 is a longitudinal-sectional view of a third
embodiment variant of a currentless switch.
DETAILED DESCRIPTION OF THE INVENTION
[0058] Referring now in detail to the figures of the drawings, in
which illustrated size ratios are only diagrammatic, and first,
particularly, to FIG. 1 thereof, there is seen a motor vehicle 11,
having at least one internal combustion engine 8 and having an
exhaust-gas treatment device 12 for the purification of exhaust
gases of the internal combustion engine 8. The exhaust gases from
the internal combustion engine 8 can be purified with an SCR
catalytic converter 14 provided in the exhaust-gas treatment device
12. The method of selective catalytic reduction can be carried out
at the SCR catalytic converter 14 using liquid additive (such as an
aqueous urea solution), which can be fed to the exhaust-gas
treatment device 12 with a feed device 13 on a delivery unit 1. The
feed device 13 has a pump 10 and a delivery line 9. The delivery
line 9 runs from an extraction point 17 on a tank 7 through the
pump 10 to the feed device 13. The direction from the tank 7 to the
feed device 13 is designated as a feed direction 18.
[0059] Furthermore, the motor vehicle 11 has a control unit or
controller 4. Active draining of the delivery line 9 of the
delivery unit 1 can be carried out with the control unit 4. The
control unit 4 is supplied with electrical energy and/or with
electrical signals through an electrical connection 2 by a supply
device or supplier 15. This electrical connection 2 has a switch 3
which is actuated as a function of temperature. When the
temperature drops resulting in a (predefined, lower) threshold
temperature being reached, the switch 3 closes the electrical
connection 2 in order to activate the control unit 4. In addition,
a deactivation switch 19 can also be provided on the electrical
connection 2. The control unit 4 can control the deactivation
switch 19 again later through a deactivation line 20 in order to
deactivate the control unit 4 independently of the position of the
switch 3. The control unit 4 can also have a memory 6 (which
acquires and/or archives electrical data) in which information as
to whether or not the delivery unit 1 has been drained is stored.
The control unit 4 is connected to the pump 10 through a control
line 16 in order to control the pump 10. It is furthermore
advantageous if the switch 3 can be bypassed and/or blocked by a
bypass 21 during operation of an internal combustion engine 8. The
motor vehicle 11 preferably also has a temperature sensor 5 which
is connected to the control unit 4 and with which the control unit
4 can independently monitor the temperature which is present, in
order to check whether or not the draining of the delivery unit 1
is actually to be carried out.
[0060] FIG. 2 shows a switch 3 which is suitable for the described
method and which is embodied as a bimetal switch 23. This bimetal
switch 23 is composed of a first metal 24 and a second metal 25
which are permanently connected to one another. The first metal 24
and the second metal 25 have different coefficients of thermal
expansion. The bimetal switch therefore deforms when the
temperature changes. The bimetal switch 23 is configured in such a
way that electrical contacts 22 make contact with one another when
a threshold temperature is reached in order to produce an
electrical connection 2.
[0061] FIG. 3 shows a switch 3 which is suitable for the described
method and which functions by using a fluid (an expansion fluid
27). The switch 3 has a reservoir 28 which is filled with the
expansion fluid 27. In order to ensure that the temperature of the
surroundings effectively passes to the expansion fluid 27, the
switch 3 also has a temperature pickup body 26 for picking up the
ambient temperature and for passing the ambient temperature on to
the expansion fluid 27. The expansion fluid 27 is connected to a
piston 29. If the temperature of the expansion fluid 27 decreases
or increases, the piston 29 moves. When a threshold temperature is
reached, the piston 29 is moved in such a way that the electrical
contacts 22 make contact with one another and an electrical
connection is produced.
[0062] FIG. 4 shows a switch 3 which is suitable for the described
method and is prestressed (mechanically). This switch 3 has an
expansion material 35 which is, for example, a metal and which is
lengthened or shortened as a function of the ambient temperature.
The expansion material 35 is mounted in a frame 31 and is located
in a first position 32 in which it is prestressed against a stop
30. The expansion material 35 which is illustrated in FIG. 4
preferably expands when the ambient temperature drops. When a
threshold temperature is reached, the expansion material 35 has
expanded to such an extent that it tips over or flips over from the
first position 32 into a second position 33. An electrical
connection is then produced between the two electrical contacts 22.
An actuator 34, with which the expansion material 35 can be reset
actively back into the first position 32, is also preferably
provided.
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