Note: Descriptions are shown in the official language in which they were submitted.
CA 02603756 2007-09-25
Reinz-Dichtungs-GmbH
D.P 230 CA
TO/sk
HEAT SHIELD CONFIGURATION
[0001] The present invention relates to a heat shield configuration having a
heat shield for
shielding an object against heat and/or noise having an internal surface
facing toward the object
and an external surface facing away from the object as well as at least one
opening, which goes
through the heat shield having internal and external surfaces. Heat shields of
this type are used,
for example, in engine compartments of motor vehicles, in particular in the
area of the exhaust
system, to protect neighboring temperature-sensitive components and assemblies
from impermis-
sible heating. The heat shields are often used simultaneously as a noise
protector. Concretely,
such heat shields may be used, for example, for shielding a catalytic
converter or pre-catalytic
converter, a particulate filter, or other components in the area of the
exhaust system or of a tur-
bocharger. In regard to continuous operation, it is often not only important
for these components
to be protected from too strong a temperature strain, but rather the operating
temperature is to be
subjected to strong oscillations during the entire operating life as little as
possible.
[0002] The most possible constant operating temperature is advantageous, for
example, for the
components used for exhaust treatment, because in this way a more uniform
exhaust treatment
effect may be achieved. Simultaneously, the service life of the components,
neighboring housing
parts, and gas-conducting components may also be lengthened. Rapid heating and
keeping the
operating temperature constant are of special significance in regard to
maintaining the future EU
exhaust gas standard Euro 5. In addition to the exhaust gas limiting values in
the normal operat-
ing phase of an engine, exhaust gas limiting values of the cold starting phase
are also incorpo-
rated here The efficiency of the exhaust treatment catalytic converters for
the pollutants con-
tained in the exhaust gas is known to differ as a function of the temperature.
Thus, for example,
the discharge of hydrocarbons and carbon monoxide is particularly high at the
beginning of the
cold start phase. This is primarily to be attributed to the fact that the
catalytic converter has not
yet reached its operating temperature. To reduce these pollutants, it is
therefore necessary to in-
CA 02603756 2014-03-26
2
crease the operating temperature of the catalytic converter as rapidly as
possible. On the other
hand, the operating temperature cannot rise too much, however, because this
results on the one
hand in the increase of other pollutants such as nitrogen oxides in the
exhaust gas, and on the
other hand, too high a temperature may damage the catalytic converter itself.
[0003] In other cases, it may be desirable, for example, to be able to set a
higher or lower tem-
perature during a specific operating phase than in other operating phases.
Thus, for example, a
particulate filter may pass through an operating phase of higher temperature
in which
accumulated particles in the particulate filter are removed by oxidation. Up
to this point,
reaching this elevated temperature by engine measures or by additional
injection of fuels was
typical. After completed particle removal, the measures were returned to
normal operation again.
However, this procedure is very complex and requires additional energy.
[0004] In consideration of the problems described above, it is the object of
the present invention
to specify a heat shield configuration which is capable of setting the
operating temperature of an
object shielded thereby to a predefined range. The heat shield configuration
is on the one hand to
allow the temperature to be kept as constant as possible and simultaneously
ensure the most
rapid possible achievement of the operating temperature. On the other hand,
the heat shield
configuration is also to allow selective operation at various predefined
temperatures.
[0005] This object is achieved by the heat shield configuration. Preferred
embodiments are
specified in the subclaims.
[0006] The heat shield configuration according to the present invention
comprises a heat shield
for shielding an object against heat and/or noise having an internal surface
facing toward the
object and an external surface facing away from the object. An opening is
provided in the heat
shield, which goes through the internal and external surfaces. According to
the present invention,
this opening is at least regionally closable by a closure, which may be opened
and closed using
an actuating device as a function of a controlled variable relevant for the
function of the object.
[0007] The opening implemented in the heat shield is exposed by opening the
closure, so that
better temperature regulation is made possible by the passage thus resulting.
For example, hot air
CA 02603756 2007-09-25
3
accumulated between the object to be shielded, which is situated neighboring
the internal surface
of the heat shield, and the heat shield may escape through the exposed opening
and thus the tem-
perature in the area around the object to be shielded may be reduced. Vice
versa, it is just as pos-
sible, for example, to introduce colder air in the direction toward the object
to be shielded
through the exposed opening and thus reduce the temperature in its
environment. It is also possi-
ble to feed hot air in the direction toward the object to be shielded through
the opened opening or
discharge cold air if its temperature increase is desired. In addition, the
opening may be at least
partially closed in an operating phase of increased temperature, while it is
at least partially ex-
posed in an operating phase of lower temperature, so that accumulated heat may
escape through
the opening. More than two operating phases of different temperatures are also
fundamentally
settable as a function of the opening size of the opening.
[00081 At least one of the following measured variables comes into
consideration as a controlled
variable which the closure is opened or closed as a function of:
- a temperature,
- a pressure,
- a velocity,
- an acoustic signal,
- an exhaust gas value,
- a volume flow, and
- an operating time.
[00091 In the preferred application of the present invention in the area of
internal combustion
engines, very generally, those measured variables which may be measured in the
area of the in-
ternal combustion engine come into consideration.
[0010] The temperature is expediently a temperature in the environment of the
object to be
shielded o: the component temperature of the object or another component, if
this temperature
has effects on the function of the object to be shielded, By measuring the
temperature, it may be
established directly whether the object to be shielded is threatened with
overheating. If so, the
CA 02603756 2007-09-25
4
actuating device may counteract this by opening the closure in the heat
shield. Vice versa, in the
event of too strong cooling, the closure may be closed again using the
actuating device.
[0011] The internal pressure of the object to be shielded may particularly be
measured as the
pressure. A possible application is in particulate filters, in which the
internal pressure rises with
increasing charging by particles. The throughput correspondingly worsens, and
the particulate
filter must be freed of the deposited particles to obtain the desired
filtering action. This may be
performed by raising the temperature in the interior of the particulate filter
so strongly that the
particles oxidize and are blown out of the filter. The required temperature
increase may be per-
formed or at least supported by closing the closure, by which heat accumulates
in the area of the
heat shield around the particulate filter. After passage of a predefined time
or alternatively upon
reaching a lower internal pressure, which allows regular operation of the
particulate filter, the
closure may be opened again, so that the operation runs at the desired filter
operating tempera-
ture.
[0012] To be able to operate the object to be shielded at a desired operating
temperature - as
noted - the temperature of the object itself may be measured directly or in
its environment. In-
stead of the temperature, however, other measured variables may also be
measured, which have
effects on the operating temperature of the object. Such a parameter is, for
example, a flow
which may result in cooling if it flows along the object to be shielded. The
closure may thus be
closed more in the event of stronger flow and opened more in the event of
lesser flow as a func-
tion of the flow velocity to set a desired operating temperature. If the
object is moved during op-
eration, the travel velocity may also be measured instead of a flow velocity.
[0013] Acoustic signals may be ascertained if the object, which produces noise
itself, is to be
shielded to the environment. In the event of stronger noise development, the
closure is expedi-
ently closed. The noise pressure is preferably measured.
[00141 Exhaust gas values may also be used as measured variables. For example,
concentrations
of one or more gases in the exhaust gas may be determined in a way known per
se. As noted at
the beginning, the effectiveness of the catalytic converter for the various
pollutants changes as a
function of the temperature. The measurement of the exhaust gas value for
these pollutants thus
CA 02603756 2007-09-25
allows conclusions as to whether the temperature is in the desired range. If
the measured exhaust
gas values deviate from predefined setpoint values, the exhaust treatment
action may be brought
back into the setpoint range by temperature correction. This is performed
according to the pres-
ent invention, for example, by opening or closing the closure and
correspondingly regulating the
opening cross-section of the opening in the heat shield as a function of one
or more measured
values of the pollutant concentration in the exhaust gas.
[0015] In addition to the cited measured variables, in principle, all those
measured variables
come into consideration which may have an influence on the function of the
object to be shielded
or contain information about the operating state or another property of the
object. The actuating
device may act as a function of only one measured variable or also as a
function of multiple
measured variables.
[0016] To measure the measured variable, the heat shield configuration
according to the present
invention expediently comprises at least one suitable measuring device. The
measuring device
may fundamentally be a typical device from the prior art for measuring the
particular measured
variable. For example, a temperature sensor may be used for temperature
measurement, which is
attached to the object to be shielded, the heat shield, or another point in
proximity to the object.
Analogously, other sensors (pressure, noise pressure, electrochemical value)
may be used, which
are already known in the prior art. Ideally, sensors which may be replaced
independently of other
parts are used. In many cases, measuring devices already present in the
overall device which
comprises the heat shield configuration according to the present invention,
such as measuring
devices for measuring exhaust gas values or vehicle velocities, may also be
used.
[0017] The heat shield configuration expediently also comprises means for
analyzing the meas-
urement results and control means for controlling the actuating device on the
basis of the analy-
sis of the measurement result. Both means may be spatially combined in one
device and may be
situated separately from or integrated in the actuating device. In each case,
these are components
known per se, which do not have to be described in greater detail here. As
already for the meas-
uring device, means present in any case in the overall device may also be used
for the analysis
and control means.
CA 02603756 2007-09-25
6
[0018] The actuating device may, for example, be a pneumatic, hydraulic, or
electrical actuating
device. Preferably, a servomotor is used as an electrical actuating device or
a vacuum unit is used
as a pneumatic actuating device. The connection between actuating device and
closure is funda-
mentally arbitrary. For example, a push rod or pull rod may be used.
[0019] The opening may either be a through opening in the heat shield or also
an opening in an
external edge area of the heat shield. Both variants may also be combined with
one another in
one heat shield. The possibility which is selected is also a function, inter
alia, of the available
space on the heat shield. The shape of the opening is fundamentally arbitrary
and is also primar-
ily a function of the available space. The size of the opening is selected as
a function of the re-
quired heat exchange and/or in regard to the desired noise insulation. The
required opening
cross-section may be implemented using one or more openings.
[0020] The closure may fundamentally have any arbitrary shape which is capable
of closing the
opening in the heat shield to the required extent. It may be inserted fitting
into the opening or
may be situated on the heat shield covering the opening. The way in which the
closure exposes
the opening is also fundamentally arbitrary. For example, the closure may be
displaced laterally
in relation to the opening and/or pivoted and/or lifted like a flap off the
opening. In the two first
cases, the closure is preferably displaced and/or pivoted predominantly
parallel to the external
surface of the heat shield using a slide. In the latter case, the closure may
fundamentally open
toward any side of the heat shield. However, for space reasons it is
frequently expedient for the
closure to open toward the side of the external surface of the heat shield,
because there is fre-
quently insufficient space on the side of the internal surface between heat
shield and object to be
shielded. The flap may also comprise multiple lamellae, which may be opened or
closed indi-
vidually or jointly. The material of the closure may be selected arbitrarily.
The closure preferably
comprises the same material as the heat shield. The closure is fastened to the
heat shield de-
pending on the type of actuation, for example, using hinges in the case of a
flap closure, a screw
or rivet connection, which simultaneously provides the rotation point, in the
case of a rotating
slide, or using guide rails in the case of a slide. A flap closure may
possibly also be fastened to
an object in proximity to the heat shield and not to the heat shield itself.
CA 02603756 2007-09-25
7
[0021] A preferred application of the heat shield according to the present
invention is, as already
noted, the shielding of components in the area of an internal combustion
engine and in particular
in the area of the exhaust system. In these applications, the danger primarily
exists that the object
to be shielded will overheat as a result of the accumulated heat in the area
of the heat shield. To
prevent this, the heat shield according to the present invention is
expediently implemented in
such a way that the closure is opened if a specific limiting temperature is
exceeded, so that the
accumulated heat may escape from the area between heat shield and object to be
shielded. As
long as the components situated in the area of the heat shield have not yet
reached their operating
temperature, however, the accumulation of heat in the area of the heat shield
is completely ad-
visable, so that the components may reach their optimal operating temperature
as rapidly as pos-
sible. For this reason, the heat shield according to the present invention is
preferably designed in
this variant in such a way that the closure remains closed until reaching the
limiting temperature.
The temperature does not have to be measured directly, as noted, but it may be
a measured value
other than the temperature.
[0022] A further preferred application is the shielding of particulate
filters, in particular diesel
particulate filters. As described, it may be expedient here to remove the
accumulated particles by
oxidation at increased temperature in a specific operating phase. Using the
heat shield according
to the present invention, the required temperature increase may be achieved
especially easily and
rapidly. In contrast to the prior art, it is frequently no longer necessary to
increase the exhaust
gas temperature by additional engine measures, although this still remains
possible. Rather, the
opening in the heat shield may be closed by closing the closure using the
actuating device. The
temperature then rises in the area of the heat shield and thus also in the
particulate filter. If this
temperature increase alone is insufficient to begin the oxidative cleaning, in
addition, the fuel/air
mixture of the engine may be adapted or fuel may be injected directly, as
usual. After completed
cleaning, the closure is opened again, the additional altered injection is
ended if necessary, and
the temperature in the area of the heat shield falls again, so that the
particulate filter may operate
further in the regular operating state
[0023] in the case of the heat shield for a particulate filter or a similar
device, the closure is ex-
pediently opened at lower temperature and closed at increased temperature.
This is preferably
CA 02603756 2007-09-25
8
reversed for the heat shield described for a catalytic converter. The closure
is closed with sinking
temperature here, while it is opened in the event of temperature increase.
Both variants may be
implemented corresponding to the requirements in the scope of the present
invention. They may
also be used jointly in the same heat shield. Moreover, in a heat shield for a
particulate filter, an
additional higher temperature limit may be defined to make the closure open in
order to prevent
overheating of the particulate filter.
[0024] It is not absolutely necessary for the closure to open suddenly if the
predefined limiting
value is exceeded, for example, and expose the opening 100 %, while the
closure is immediately
completely closed and completely covers the opening at a value of less than or
equal to the lim-
iting value. Rather, it is also possible that the opening and closing of the
closure occurs within a
predefined limiting measured value interval. For example, it may be advisable
for the closure to
increasingly expose the opening with increasing deviation from the predefined
limiting value, so
that, for example, with increasing temperature (with more strongly deviating
measured value), an
increasing temperature exchange with the environment is possible. Vice versa,
the opened clo-
sure may be increasingly closed again if the increased temperature (or another
measured value)
falls in the direction toward the limiting value again. In this way, a
continuous temperature con-
trol adapted to the ambient temperature (or the relevant measured value) is
possible, which al-
lows the object to be shielded by the heat shield to be kept at an essentially
constant operating
temperature which is optimal for this object. Closing the opening does not
have to result in a
hermetic seal of the opening. A significantly reduced temperature exchange in
relation to the
opened state is generally sufficient. The above statements also apply for the
case of opening
upon sinking (temperature) measured value and closing upon higher
(temperature) measured
value.
[0025] The range in which the limiting measured value is set, in which the
closure in the heat
shield configuration according to the present invention opens or closes, is
mainly a function of
the temperature at which the object which is to be shielded using the heat
shield according to the
present invention is to be kept. In the case of catalytic converters, this is
expediently the tem-
perature at which the best exhaust gas reduction is possible. For particulate
filters, on the one
hand the optimal temperature for particle filtration and on the other hand the
best temperature for
CA 02603756 2007-09-25
9
oxidative removal of the particles in the particle removal phase may be set.
This particular opti-
mal operating temperature may be achieved very rapidly using the heat shield
configuration ac-
cording to the present invention, because heat may be accumulated in the area
around the object
to be shielded in the warm-up phase by closing the opening using the closure,
so that the object
heats rapidly. On the other hand, exceeding an optimal operating temperature
too strongly may
be prevented by setting the limiting measured value appropriately, upon
exceeding which the
closure in the heat shield is opened and thus exposes the opening entirely or
partially depending
on the measured value. Heat accumulated between heat shield and object to be
shielded may es-
cape through the exposed opening. Additionally or alternatively, it is
possible to inject cool air
through the opened opening in the direction toward the object to be shielded
(such as the cata-
lytic converter, particulate filter, etc.), to cool it.
[0026] Especially good regulation of the temperature in the area between heat
shield and object
to be shielded is possible if in addition to the first opening having the
first closure at least one
further opening is provided, which is also closable using a closure to be
opened and closed as a
function of a measured variable relevant for the function of the object to be
shielded. This meas-
ured variable may, but does not have to be the same measured variable as for
the first closure.
[00271 The further closure may fundamentally be implemented as described
above. It may also
be opened and closed by an actuating device, as was described above. However,
it is also possi-
ble to leave out the actuating device and use a closure opening and closing
automatically as a
function of a measured variable. This is preferably a closure opening and
closing as a function of
the temperature. The closure therefore expediently has a bimetallic element,
which deforms as a
function of the temperature. The bimetallic element may be a part of the
closure which deforms
in relation to the opening, or a separate part which works together with a
slide, rotating slide, or
flap and displaces it in relation to the opening.
[0028] The presence of at least one further closure and an opening closable
thereby has the ad-
vantage that the temperature in the area between heat shield and object to be
shielded may be set
even more precisely. For example, it is possible to implement the actuating
device(s) and clo-
sures in such a way that the latter open in sequence if various limiting
measured values are ex-
ceeded. This may be achieved by storing various limiting measured values and
corresponding
CA 02603756 2007-09-25
differing activation of the closures. The closures may be opened in sequence,
for example, in
such a way that the exposed total opening cross-section of the openings rises
with increasing
temperature, so that increasingly more hot air may escape through the exposed
opening. Over-
heating may thus be prevented even in the event of very strongly rising
temperatures.
[0029] A further advantage which may be achieved by providing multiple
openings closable us-
ing a closure is that targeted flow guiding is possible in the space between
heat shield and object
to be shielded. For example, cooler air may be introduced in the direction
toward the object
through one or more of the exposed openings if the closure is opened, while
heated air flows out
through the remaining openings. The openings and closures on the heat shield
are expediently
oriented in such a way that the hot air flowing out is not directed toward
temperature-sensitive
parts situated in the surroundings of the heat shield. Ideally, the hot
exhaust air is directed in
such a way that it is fed to an external flow existing in the area around the
heat shield and is con-
veyed thereby. It is also advantageous if the cooler air introduced into the
area between heat
shield and object to be heated is fed from this external flow existing in the
area around the heat
shield.
[00301 As already described above, it is also possible in the case of feeding
cooler air into the
area between heat shield and object to be shielded that various closures open
for the feeding of
cooler air at different temperatures. This is also fundamentally true for the
closures through
which the heated air flows out. In this way, a very constant temperature may
be ensured in the
area between heat shield and object to be shielded over a large temperature
range. Additionally
or alternatively to these measures, it is also possible that the closures for
the feeding of cooler air
open at a different temperature than the closures for the exhaust of heated
air. In the latter case, it
is preferable for the feed closures to open at a somewhat higher temperature
than the closures for
the exhaust of hot air.
f00311 The heat shield according to the present invention is not restricted to
special shapes or
sizes. For example, it may be a planar heat shield, which is attached above
the object to be
shielded, so that hot air accumulates below the heat shield. The present
invention is especially
suitable for a heat shield which essentially encloses the object to be
shielded on all sides. A corn-
CA 02603756 2007-09-25
11
parable effect may also be achieved if a heat shield open on one side is
closed by an adjoining
component. The object to be shielded is thus largely encapsulated by the heat
shield aid possibly
other components. This typically does not represent a hermetic enclosure,
because hermetically
terminated passages for supply lines and drain lines are typically not
provided in the heat shield.
Nonetheless, the heat exchange with the environment is relatively restricted
in these cases, so
that overheating of the components encapsulated in the heat shield may occur
very rapidly. On
the other hand, the cold start phase is relatively short, because the desired
operating temperature
is achieved rapidly by the heat retention inside the heat shield. This optimal
operating tempera-
ture may be kept constant in a desired range easily using the heat shield
configuration according
to the present invention by the provision according to the present invention
of at least one open-
ing which is closable by a flap opening and closing as a function of a
measured variable. The at
least one heat shield, which essentially completely encloses the object to be
shielded, addition-
ally ensures especially good noise insulation.
[0032] The measures suggested according to the present invention may be
implemented easily
and cost-effectively without additional complicated measures or components in
typical heat
shields. The main bodies of the heat shield according to the present invention
may thus funda-
mentally correspond in their implementation to those which are already known
from the prior art.
Size, shaping, and materials thus correspond to the prior art. Heat shields in
sandwich construc-
tion, which comprise two outer layers typically made of metallic material and
an insulating layer
embedded between them, are preferred. The surfaces may be smooth, textured, or
perforated.
Heat shields of this type are described, for example, in DE 3834054 Al and EP
1775437 Al
(European Patent Application 05022095.3) of the applicant. Furthermore,
reference may be made
to GB 2270555 A and US 2004/0142152 Al.
[0033] The present invention may fundamentally be applied to all heat shields
of the prior art.
The present invention is especially suitable for those heat shields which are
used in the area of
high temperature development and for shielding those objects which may be
damaged by excess
temperature. A preferred use of the heat shields according to the present
invention is therefore in
the area of internal combustion engines and particularly in the area of the
exhaust system here.
Examples of preferred heat shields are those for catalytic converters, pre-
catalytic converters.
CA 02603756 2007-09-25
12
diesel particulate filters, or also turbochargers. The present invention may
additionally be applied
in particular to metallic subfloors or their components in the area of an
exhaust system.
[0034] The present invention is explained in greater detail in the following
on the basis of
drawings. These drawings are exclusively used to illustrate preferred
exemplary embodiments of
the present invention, without the present invention being restricted thereto.
Identical parts are
provided with identical reference numerals in the drawings.
[0035] In the figures:
Figure 1(a): schematically shows a cross-section through a first exemplary
embodiment of a
heat shield configuration according to the present invention for shielding a
cata-
lytic converter having closed closure;
Figure 1(b): schematically shows the heat shield configuration from Figure
1(a) having opened
closure;
Figure 2(a): schematically shows a cross-section through a second exemplary
embodiment of a
heat shield configuration according to the present invention for shielding a
cata-
lytic converter having two closed closures;
Figure 2(b): schematically shows the heat shield configuration from Figure
2(a) having one
open and one closed closure;
Figure 2(c): schematically shows the heat shield configuration from Figure
2(a) having two
open closures;
Figure 3(a): schematically shows a cross-section through a third exemplary
embodiment of a
heat shield configuration according to the present invention for shielding a.
cata-
lytic converter having one closed closure, the heat shield being open on one
side;
Figure 3(b): schematically shows the heat shield configuration from Figure
3(a) having open
closure;
CA 02603756 2007-09-25
=
13
Figure 4: schematically shows a block diagram to explain the activation of
an actuating de-
vice:
Figure 5: schematically shows a partial cross-section through a further
exemplary embodi-
ment of a heat shield configuration according to the present invention in the
area
of a closure;
Figure 6: schematically shows a top view of a further exemplary embodiment
of a heat
shield configuration according to the present invention and a catalytic
converter
thus shielded, and
Figure 7: schematically shows a top view of still a further exemplary
embodiment of the
heat shield configuration according to the present invention and a catalytic
con-
verter thus shielded.
[0036] Figures 1(a) and 1(b) show a first exemplary embodiment of a heat
shield configuration
according to the present invention having a heat shield 1, which is used for
shielding a catalytic
converter 2 situated in the interior of the heat shield 1. The catalytic
converter 2 may be, for ex-
ample, a catalytic converter for treating exhaust gases of an internal
combustion engine of a mo-
tor vehicle. The exhaust treatment action of the catalytic converter 2 is best
within a specific
temperature range. This temperature range is to be reached as rapidly as
possible, but is not to be
exceeded. The catalytic converter 2 is enclosed essentially completely and on
all sides by the
heat shield 1. In this way, the catalytic converter 2 and its envirotunent are
insulated especially
well from one another in regard to temperature influences and noise. In
addition, the encapsula-
tion is used so that the catalytic converter 2 reaches the operating
temperature required for opti-
mal exhaust treatment rapidly. The cold start phase may thus be shortened by
rapid temperature
increase in the interior of the heat shield 1, which is a significant
advantage in regard to the ex-
pected exhaust gas standard Euro 5.
[0037] Figure 1(a) shows the heat shield 1 having the catalytic converter
situated in its interior
during the watin-up phase to the optimal operating temperature of the
catalytic converter 2. In
this phase, the closure 6, which is located on the top side of the heat shield
and encloses an
CA 02603756 2007-09-25
' =
14
opening present there in the form of a through opening in the heat shield, is
completely closed.
The heat generated during operation of the internal combustion engine
therefore remains in the
interior of the heat shield 1 and heats the catalytic converter rapidly to the
desired operating tem-
perature.
[0038] In the case shown, the closure 6 completely comprises a flap 13. The
flap is expediently
manufactured from the same material as the heat shield 1 and is fastened
thereto using at least
one hinge. Above a specific limiting temperature (or another measured variable
representative
for the temperature in the environment of the catalytic converter), the flap
13 is opened using an
actuating device 7 in the form of a positioning motor. To be able to establish
reaching the limit-
ing temperature, a temperature sensor 8 is fastened to the inside 3 of the
heat shield 1. After an
analysis described later in connection with Figure 4, the actuating device 7
comes into action if
exceeding the fixed limiting temperature is established and opens the flap 13,
which is connected
to the rod 14, via a push and pull rod 14. This is shown in Figure 1(b).
[0039] With rising temperature in the interior of the heat shield 1 and
correspondingly increasing
opening by the actuating device 7, the closure 6 exposes an increasingly
larger opening cross-
section of the through opening 5. The opening of the closure 6 and the
exposure of the through
opening 5 upon exceeding the predefined limiting temperature ensure that heat
accumulated in
the interior of the heat shield 1 may escape through the through opening, as
illustrated by the ar-
rows. Overheating of the catalytic converter 2 in the interior of the heat
shield 1 is thus avoided.
If the temperature in the interior of the heat shield 1 sinks again, the
actuating device 7 closes the
closure back in the direction toward the starting situation shown in Figure
1(a). The through
opening 5 is closed by the closure 6 again. In this way, too strong reduction
of the temperature in
the interior of the heat shield 1 is prevented. Another cold start of the
engine would again occur
with closed closure 6, so that the catalytic converter 2 in the interior of
the heat shield 1 may
again be brought rapidly to the required operating temperature. These
procedures are repeatable
arbitrarily often with good reproducibility, so that optimum operating
conditions of the catalytic
converter may be ensured with very good noise protection simultaneously.
CA 02603756 2007-09-25
=
[OM] Figures 2(a) through 2(c) show a refinement of the heat shield
configuration from Figures
1(a) and 1(b). In addition to the first closure 6, a further closure 6a is
provided in the heat shield
1, which may close a further through opening 5a in the top area of the heat
shield 1. The fur.
tional principle cf both closures corresponds to that of the preceding
exemplary embodiment. For
simplification, the measuring device 8 is no longer shown.
[0041] Figure 2(a) shows the state of the heat shield 1 in the warm-up phase.
Both closures 6 and
6a are closed, so that the heat remains in the interior of the heat shield 1
and contributes to rap-
idly reachiqg the operating temperature of the catalytic converter 2. Above a
first limiting tem-
perature., which may restlt in overheating of the catalytic converter 2
especially in full load op-
eration, the first closure 6 is opened in the way described above and exposes
the through opening
5 on the top right side of the heat shield 1, so that the hot air indicated by
the arrows may escape
from the interior of the heat shield 1. The second closure 6a is still closed
in this phase. It is first
opened by the second actuating device 7a upon further temperature increase in
the interior of the
heat shield 1. This is shown in Figure 2(c). To achieve the opening of the
closures 6 and 6a at
different limiting temperatures, the actuating devices 7, 7a are activated in
such a way that they
open at different limiting temperatures. Cooler air may enter through this
through opening into
the interior of the heat shield 1 due to the exposure of the through opening
5a. The colder air
flows along the top side of the catalytic converter 2, cools it, and entrains
hot air through the
through opening 5 on the top right side of the heat shield out of its
interior. In this way, effective
cooling of the catalytic converter is possible even at very high exhaust gas
temperature. The ex-
emplary embodiment described thus allows the catalytic converter to operate
under essentially
constant temperature conditions even in the event of relatively strongly
oscillating exhaust gas
temperature.
[0042] Figures 3(a) and 3(b) show an alternative heat shield configuration, in
which the heat
shield 1 does not completely enclose the catalytic converter 2, but rather is
open on its bottom
side. The lower edge only has a small distance to the neighboring component
15, which radiates
heat in operation of the engine. The measuring device 8 is again not
illustrated. As in the exem-
plary embodiment from Figures 1(a) through 1(c), the heat shield only has one
closure 6. The
small distance between heat shield 1 and neighboring component 15 accelerates
the achievement
CA 02603756 2007-09-25
=
16
of the operating temperature of the catalytic converter 2 with closed closure
6. Upon reaching the
limiting temperature, the closure 6 is opened by the actuating device 7, as
shown in Figure 3(b).
The hot air from the interior of the heat shield may escape through the
opening 5. The suction
thus arising causes cooler air to flow behind through the space between heat
shield 1 and neigh-
boring component 15, so that an optimal operating temperature of the catalytic
converter 2 is en-
sured in spite of the heat radiated by the component 15. The space between
heat shield 1 and
neighboring component 15 may be tailored - insofar as this is possible in the
existing space - to
this operating temperature of the catalytic converter 2 and the radiation of
the component 15.
[0043] Figure 4 illustrates the sequence upon actuation of the closure 6 using
the actuating de-
vice 7 in the forin of a block diagram. A measuring device 8 ascertains
measurement data for a
measured variable relevant for the function of the object 2 to be shielded
continuously or at fixed
intervals. This may be the temperature in the environment of the catalytic
converter, for example.
The ascertained measured data is transmitted in a way known per se to an
analysis unit 9 and
analyzed there. The analysis unit compares the measured data to a previously
established limiting
value, such as a limiting temperature. If the analysis unit 9 establishes that
the limiting value has
been exceeded, it transmits the result to the control unit 10. In turn, this
transmits a control signal
to the actuating device 7, because of which it opens the closure 6 to the
predefined extent. The
closing procedure runs correspondingly, if it is established the temperature
falls below the limit-
ing temperature. Analysis and control units may also be unified in a shared
device and installed
in the heat shield configuration separately from or jointly with the measuring
device 8.
[0044] In the case of a particulate filter, a measuring apparatus 8 may be for
the pressure in the
interior of the particulate filter. The ascertained measured data is compared
to a previously es-
tablished base pressure by the analysis unit 9 in this example. If this
pressure is exceeded, this is
relayed via the control unit 10 to the actuating device 7, on the basis of
which it closes the clo-
sure 6 in the predefined procedure. This opening procedure runs
correspondingly if the pressure
falls below the limiting pressure after oxidative regeneration of the
particulate filter, for example.
A second limiting pressure may also be established, which is below the first
limiting pressure for
the closing. The sequence for other measured signals runs comparably.
CA 02603756 2007-09-25
17
[0045] Figure 5 shows a partial section of a further embodiment of the present
invention in the
area of the closure 6, which may be opened and closed by an actuating device
7. The mode of
operation corresponds to those of the preceding figures. The curves of the
heat shield 1 and the
closure 6 are adapted to the external contour of the object to be shielded,
whose external outline
is illustrated by the line 16. By tailoring the curves, the heat shield having
closure 6 may be
brought very close to the object to be shielded. The solid line at 6
illustrates the open position of
the closure, and the dashed line lying underneath illustrates the closed
position of the closure.
[0046] Figures 6 and 7 show alternative embodiments of the closure 6. Figure 6
shows an em-
bodiment in which the opening 5 in the heat shield 1 is a recess in the
external edge area. The
opening 5 is closable using a slide 11 as the closure 6. The closure 6 may be
displaced in the di-
rection of the arrow using the actuating device 7. A situation having almost
completely open clo-
sure and nearly completely exposed opening 5 is shown.
[0047] Figure 7 shows an embodiment similar to Figure 6, but having a rotating
slide 12 as the
closure 6. The rotating slide is fastened to the heat shield 1 at a point 17
using screw or rivet
connections and is mounted at this point so it is rotatable. By actuating the
actuating device 7,
namely by extending the rod 14, which is fastened to the rotating slide 12 so
it is rotatable at the
point 18, more or less, the rotating slide may be pivoted around the point 17,
as is illustrated by
the double arrow. The through opening 5 in the heat shield is correspondingly
covered more or
less by the rotating slide 12.
