U.S. patent application number 14/392043 was filed with the patent office on 2015-09-17 for heat shield.
The applicant listed for this patent is REINZ-DICHTUNGS-GMBH. Invention is credited to Franz Schweiggart.
Application Number | 20150260075 14/392043 |
Document ID | / |
Family ID | 49680991 |
Filed Date | 2015-09-17 |
United States Patent
Application |
20150260075 |
Kind Code |
A1 |
Schweiggart; Franz |
September 17, 2015 |
HEAT SHIELD
Abstract
The present invention relates to a heat shield for shielding of
hot areas of a part. Such heat shields are for instance used for
shielding hot areas of combustion engines, especially of catalysts,
exhaust manifolds, turbo chargers and the like or also in the
conditioning of batteries. Conventionally, they comprise at least
one metallic sheet layer. In addition to this metal sheet layer,
which renders stability to the heat shield, typically an insulating
layer made of insulating material, e.g. porous material is provided
as a further layer.
Inventors: |
Schweiggart; Franz;
(Pfaffenhofen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
REINZ-DICHTUNGS-GMBH |
Neu-Ulm |
|
DE |
|
|
Family ID: |
49680991 |
Appl. No.: |
14/392043 |
Filed: |
November 14, 2013 |
PCT Filed: |
November 14, 2013 |
PCT NO: |
PCT/EP2013/073870 |
371 Date: |
May 6, 2015 |
Current U.S.
Class: |
165/185 |
Current CPC
Class: |
F16L 59/08 20130101;
F01N 2310/02 20130101; B60R 13/0876 20130101; B32B 3/26 20130101;
F16L 59/029 20130101; F01N 13/14 20130101; B32B 15/14 20130101;
F01N 2260/022 20130101; B32B 3/30 20130101 |
International
Class: |
F01N 13/14 20060101
F01N013/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2012 |
DE |
20 2012 010 993.6 |
Claims
1-19. (canceled)
20. A heat shield for shielding of hot areas of a part with at
least one metallic layer and an insulating layer having a porous
insulating material arranged at least in sections adjacent to the
metallic layer, comprising: at least one flow channel formed into
the porous insulating material of the insulating layer on its
surface pointing away from the metallic layer, the channel extends
as a groove on the surface of the insulating layer which points
away from the metallic layer.
21. The heat shield of claim 20, wherein the insulating layer
extends over at least 90% of the planar extension of the metallic
layer.
22. The heat shield of claim 20, wherein the heat shield is
comprised of several partial shells, which in the installed state
encircle the part in an annularly closed manner.
23. The heat shield of claim 20, wherein the metallic layer is a
sheet selected from the group consisting of a stainless-steel
sheet, a fire-aluminated steel sheet, and an aluminum-plated steel
sheet.
24. The heat shield of claim 20, wherein the insulating material is
a fleece that has been reinforced with a ceramic binder or a fleece
that is moulded to a shaped part.
25. The heat shield of claim 20, wherein the insulating material is
selected from the group consisting of a glass fiber fleece, an
expanded mica wool, a basalt rock wool, a ceramic mass, an expanded
clay, a high-temperature foam, and combinations of the foregoing in
layers of different materials.
26. The heat shield of claim 20, wherein the insulating layer at
least in areas is surface-treated to achieve a reinforced surface,
the surface treatment selected from a group consisting of a
ceramic-based high-temperature adhesive, coating with a
ceramic-based high-temperature lacquer, impregnating with a
material and treating by compression under elevated
temperature.
27. The heat shield of claim 20, wherein one or several flow
channels are formed in the surface of the insulating layer in such
a way that they extend distanced to each other.
28. The heat shield of claim 27, wherein the distance between
individual sections of a flow channel and/or the distance of
several flow channels relative to each other in areas with a higher
thermal load of the heat shield is smaller than in areas with a
smaller thermal load.
29. The heat shield of claim 20, wherein a housing has a laminar
self-contained hollow shape to take up the hot areas.
30. The heat shield of claim 20, wherein one or several of the flow
channels are distanced to each other and encircle the hollow space
at least once in a surrounding manner.
31. The heat shield of claim 29, wherein the housing is closed so
that at least a part of the flow channels at an interface, at which
the housing is closed, pass over in a flush manner.
32. The heat shield of claim 20, wherein at least two flow channels
are formed which surround the part independent of each other.
33. The heat shield of claim 20, wherein at least one flow channel
is helically disposed about the part and shows a varying distance
between convolutions of the helix with respect to the main
direction of the helix.
34. The heat shield of claim 20, wherein the groove forming one
flow channel at least on a section of its longitudinal extension
shows a cross-section selected from the group consisting of
rectangular, quadratic, trapezoidal and semi-circular.
35. The heat shield of claim 20, wherein the groove forming a flow
channel at least on a section of its longitudinal extension shows a
cross section that tapers in a conical manner and/or that shows a
cross section which along the groove in sections tapers and in
sections widens.
36. The heat shield of claim 20, wherein the heat shield further
comprises at least one device for an active or passive closing
and/or ventilation of at least one of the flow channels.
37. The heat shield of claim 20, wherein the heat shield shields
parts of an internal combustion engine, selected from the group
consisting of an exhaust manifold, a unit for exhaust treatment, a
unit for the supercharging of heat exchangers, a unit for the
heating of transmission oil, a unit for heating of the passenger
room, and a unit for the battery conditioning.
38. The heat shield of claim 20, wherein the heat shield is
arranged at the part so that the insulating layer with its surface
pointing away from its metallic layer at least in sections rests on
the surface of the part and in these areas the surface of the part
together with the grooves of the flow channels at least in sections
forms the flow path for a fluid or delimits such.
39. The heat shield of claim 20, wherein the groove extends from
one end of the insulating material, across the insulating material
to a second end of the insulating material.
40. The heat shield of claim 20, wherein the channel is located on
the surface of the insulating material so the channel directly
faces the part to be shielded.
41. The heat shield of claim 20, wherein the metallic layer is a
sheet selected from the group consisting of a smooth metal sheet
and a steel sheet that is dimpled at least in sections.
Description
[0001] The present invention relates to a heat shield for shielding
of hot areas of a part. Such heat shields are for instance used for
shielding hot areas of combustion engines, especially of catalysts,
exhaust manifolds, turbo chargers and the like or also in the
conditioning of batteries. Conventionally, they comprise at least
one metallic sheet layer. In addition to this metal sheet layer,
which renders stability to the heat shield, typically an insulating
layer made of insulating material, e.g. porous material is provided
as a further layer.
[0002] As far as the insulating layer is not embedded between the
two metal sheets, the insulating layer is applied with its entire
surface to the part to be shielded so that it rests to the
latter.
[0003] The operation of combustion engines and the like are subject
to variations in load, which results in a varying heat production
over the operation time. It is for instance necessary to heat up
the combustion engine immediately after its cold start to high
temperatures, in order to keep emissions and consumption at a
minimum. To this end, an insulation is provided which prevents the
heat radiation and convection of the hot or heating part to the
widest extent. On the other hand, when the combustion engine
reaches its full load operating condition, it is necessary to
provide for a heat radiation or convection as high as possible in
order to prevent the hot part or its elements from overheating.
This is of particular importance if these parts are not durable
against high temperatures.
[0004] Given the priority of the protection against overheating for
the shielded part and of the durability of the heat shield itself,
it is often necessary in the heat shield arrangements according to
the state of the art, to design them in such a manner that the
emission reduction at cold starting cannot be considered at all or
only to a small extent. However, with newer vehicles, especially
also with hybrid vehicles, operational conditions with partial load
and operational phases with frequent new starts predominate. For
this reason, it is important to consider these operational
conditions to a larger extent in the design.
[0005] This is the starting point of the present invention, which
objects on providing a heat shield with which an excellent
insulation can be achieved in all operational conditions but at the
same time allows for a sufficient heat removal at high heat load.
The present invention also relates to a component assembly with a
heat-emitting part, which is arranged at a heat shield according to
the present invention.
[0006] This object is solved by a heat shield according to claim 1
and the component assembly according to claim 19. Advantageous
embodiments of the heat shield according to the invention are given
in the dependent claims.
[0007] The present invention solves the problems described above by
providing a heat shield for shielding of hot areas of a part, which
comprises at least one metallic layer. Adjacent to this metallic
layer, a further insulating layer is arranged which extends in the
plane of the layer essentially parallel to the metallic layer.
Thus, the insulating layer extends between the part to be shielded
and the metallic layer. Both of these layers preferably follow the
outer shape of the part to be shielded. The insulating layer
consists of porous insulating material or comprises such.
Advantageously, on the surface of the insulating layer which faces
away from the metallic layer, no further layers are arranged or
only layers which are formed according to the contour of the
insulating layer, so that the insulating layer comes to rest on the
hot part directly or indirectly. The insulating layer on its
surface which faces away from the metallic layer comprises at least
one flow channel. The flow channel is formed as a groove into the
surface of the insulating layer.
[0008] If the insulating layer with its entire surface--the one
surface pointing towards the hot part--rests on the hot part, the
hot part together with the walls of the groove delimits the flow
channels in the insulating layer. At high temperatures of the hot
part, convection between the hot part and the insulating layer
takes place through these flow channels, which guides the heat
between the hot part and the insulating layer to the outside,
especially if the part shows a high temperature.
[0009] Thus, the flow channels according to the invention are
directly integrated into the porous insulating material. As they
are formed as grooves which are closed when the heat shield comes
to rest on the hot part and thereby build up the flow channels, it
becomes possible to introduce the flow channels in a simple manner
into the insulating layer. With the heat shield according to the
invention, it is advantageous that for instance with a cold part,
the convection between this part and the heat shield is small and
therefore only little heat is discharged. If the part has however
reached a high temperature, an increased heat removal takes place
via the integrated flow channels of the heat shield.
[0010] With regard to a most simplified manufacturing and fastening
of the heat shield, it is preferred if it consists in several
partial shells, which are connected to each other to form a heat
shield which annularly surrounds the part. It is especially
advantageous if the heat shield is constructed from two half-shells
which each consists in a metallic layer on their outside and an
insulating layer on their inside. It is however also possible to
combine a larger number of partial shells to an annularly closed
heat shield. It is particularly preferred if the housing formed by
the partial shells is closed in such a manner that at least a part
of the flow channels at the interface, at which the housing is
closed, pass over in a flush manner. The partial shells are for
instance connected to each other after having been mounted around
the part. In this case, connection is in particular performed at
the collar-shaped protrusions which are provided in all partial
shells at their edge regions. In the same way, it is possible to
install the partial shells individually. In a further advantageous
embodiment, at least two half-shells are connected to each other
via a kind of hinge, so that the heat shield can be mounted as a
whole. The hinges used in this context can be separately produced
parts via which the partial shells are connected to each other. It
is however also possible, that the heat shield comprises bending
areas which are provided as integral structure in the metallic
layer of the heat shield. In this case, the partial shells directly
cohere with each other and therefore are no separate parts.
[0011] It is preferred if at least one of the flow channels
comprises at least one device for active or passive opening and
closing or ventilation. In advantageous embodiments, the flow
channels at their entrances and outlets can have a closing and
opening function and this way can be switched on or off. This
enables a control of the surface temperature of the hot part. To
this end, one advantageously uses a control circuit with a
temperature sensor, e.g. at the hot part or at the heat shield,
especially at its surface. In order to control the flow channels,
it is also possible to use actuators or thermo-sensitive materials
which are able to close or open the channels due to their
temperature-controlled agility. An opening of the channels has to
be ascertained especially under full load conditions in order to
achieve an improved heat removal.
[0012] The passage of gas or air through the flow channels is
either achieved in a passive manner using natural convection or in
case of an engine of a vehicle or additionally using the slip
stream or by an active blowing of the gases, e.g. using a fan. It
is further possible to condition the gas in advance. To this end,
it can be heated using an electrical heating or using phase change
materials. As an alternative, it can be cooled using the air
condition of the vehicle prior to passing through the channels of
the heat shield.
[0013] Advantageously, the insulating material consists in a
fleece, which is for instance reinforced with a ceramic binder.
Such a fleece can be molded to a preform. It is also possible to
simultaneously mold the flow channels into the surface of the
fleece which faces away from the metallic layer. If desired, an
additional surface treatment can be provided for, e.g. using a
ceramic-based high-temperature adhesive or a ceramic-based
high-temperature coating or lacquer, in order to reinforce the
surface of the insulation layer by forming a kind of skin. Such
high-temperature adhesive, coatings and lacquers can for instance
be materials, which at temperatures between 150.degree. C. and
250.degree. C. tend to form a skin.
[0014] As insulation materials, glass mats, especially made from
SiO.sub.2, Al.sub.2O.sub.3 and/or CaO with a binder; expanded mica,
basalt rock wool, all kinds of ceramic masses, expanded clay or
high-temperatures such as polyimide or melamine are suited.
Sandwich constructions, especially with at least one of the
materials mentioned before are possible, too.
[0015] Formation and arrangement of the flow channels can be done
in different manners, which have to be adapted to the thermal
needs, which may be assessed using thermography of the hot part to
be shielded. In this respect, the flow channels have to be adapted
to the requirements in removal of heat in the hot part and in cases
also to the need of heat removal in particular areas of the hot
part, the so-called hot spots. The flow channels can show various
patterns on the surface of the insulating layer, e.g. along the
longitudinal extension of the heat shield or also transverse to it,
helical in the shape of a one-level thread or a two-level winding
and/or in the shape of several flow channels which are oriented in
counter flow relative to each other. In most cases, it is
preferable if the heat shield does not comprise a single flow
channel only but that at least two flow channels are formed in the
insulating layer which channels surround the part independent of
each other. The distances of the flow channels can be adapted to
the respective need in heat removal. Thus, they may be arranged
closer to each other in the area of hot spots. The cross sections
of the flow channels may be constant over their course or can be
varied along their course with respect to their height and/or
width, resulting in an adaptation to the local requirements. The
total length of the flow channels, the pattern of the flow
channels, a possible pooling of several flow channels at their
inlet or outlet to a single channel and the like can be adapted to
the respective requirements. It is especially advantageous if the
channels in the partial shells are formed flush to each other, so
that the flow of the gas is realized all around the entire part. If
only such channels are given which extend in the longitudinal
extension direction of the heat shield, this is of course not
required.
[0016] Especially in areas of a hot spot, it can be advantageous to
enlarge the width of a channel extending in this area, and
preferably to simultaneously reduce its height. With this, the
contact area between gas and part is increased and the heat
transfer to the gas and the heat removal are improved. The cross
section of the flow channels can in particular in the area of hot
spots can also considerably vary in the flow direction of the gas,
showing varying cross sections, so that the gas experiences
turbulences, which improves the heat transfer to the gas.
[0017] To improve cooling performance and to homologize the outside
thermal map of the entire heat shield, it can be advantageous to
provide at least a first winding on the hot side of the insulating
layer (as already described) and a at least a second winding on the
outer surface of the insulating layer resulting at least in a first
cooling circuit on the inner surface of the insulating layer and at
least a second cooling circuit on the outer surface of the
insulating layer. This enables to run the first and second cooling
circuits in different directions or in the same direction. The
first cooling circuits can run in parallel to the second cooling
circuits, thus without shift relative to the plane of the surface
of the insulating layer or be staggered. Further, they can extend
relative to each other like a double helix or in a manner crossing
each other in a projection into the middle of the insulating layer
at several places. It is particularly preferred if the airflow
passes the second cooling circuit(s) resulting from the second
winding(s) on the outer surface of the insulating layer, as this
guarantees for a simple and permanent cooling during operation of
the vehicle while no cooling takes place during rest phases of the
vehicle which facilitates the warm-up. Using first and second
cooling circuits on the inner and outer surface of the insulating
layer allows for further opportunities in designing the thermal map
according to the requirements of each special operation
condition.
[0018] Instead of forming the at least one first winding on the
inner surface of an insulating layer and the at least one second
winding on the outer surface of the same insulating layer, it is
also possible to achieve a comparable design using a sequence of at
least three insulating layers, the inner one with recesses for the
at least one first winding, the second one being continuous and the
outer one with recesses for the at least one second winding.
[0019] Cross sections with an area of 10 to 500 mm.sup.2,
advantageously of 30 to 200 mm.sup.2 are particularly suited for
the flow channels. The distances between individual flow channels
can advantageously range between 5 and 100 mm, further
advantageously between 10 and 50 mm.
[0020] In case of flow channels arranged in a thread-like manner,
which continue over several partial shells, their slope can be
between 25 and 100 mm, in particular about 50 mm. The width of the
channel advantageously ranges between 3 and 30 mm, more
advantageously between 4 and 20 mm and most advantageously between
8 and 12 mm. For the channel height, 2 to 20 mm, advantageously 5
to 15 mm and more advantageously 5 to 10 mm are especially
suited.
[0021] The cross sectional shape of the flow channels can vary as
well and be adapted to the actual requirements, e.g. by use of a
semi-circular, rectangular or a trapezoidal cross section. In case
of a trapezoidal cross-section, the longer basic side can either be
arranged on the side of the hot part or opposite to it.
Omega-shaped cross sections are possible, too. The arrangement of
the flow channels along the hot part is especially preferred, as
this results in a good cooling. However, an inclined orientation,
at an angle of between 5 and 45.degree., advantageously about
20.degree. relative to the longitudinal direction of the part is
suited, too. In a preferred embodiment, the groove forming a flow
channel at least on a section of its longitudinal extension can
show a cross section that tapers, advantageously tapers in a
conical manner. Further, this cross section can taper and widen in
sections along the groove.
[0022] It is not necessary that the insulating layer shows the same
extension as the at least one metallic layer. Rather, edge areas
may be free of insulating material especially if they only aim on
the fixation of the heat shield via its metallic layer to the hot
part. However, it is preferred that the insulating extends over at
least 50%, preferably at least 80%, preferably at least 90% of the
planar extension of the metallic layer.
[0023] The at least one metallic layer comprises or consists in a
steel sheet, in particular a stainless-steel sheet, an aluminated
steel sheet, in particular a fire-aluminated steel sheet and/or an
aluminum-plated steel sheet or the like. The metal sheet can have
the form of a smooth metal sheet or it can be dimpled at least in
sections. It is most preferred that the outer surface of the at
least one metallic layer has a good reflectivity. As a consequence,
the heat shield according to the invention combines reflection,
convection and insulating properties and allows for a tailored
design to the particular application.
[0024] The heat shield according to the invention is used for
shielding of hot parts, in particular of parts of an internal
combustion engine, especially in vehicles, thus mainly in passenger
cars and utility vehicles. The heat shield is thus particular
suitable for applications in the exhaust line, in particular at the
exhaust manifold or for the unit for exhaust treatment, the unit
for supercharging as well as for heat exchangers, for instance heat
exchangers for the heating of transmission oil, in the additional
heating for the passenger room and/or in the battery
conditioning.
[0025] In the following, some examples of heat shields according to
the invention are given. In all these examples the same or similar
reference numbers are used for identical or similar elements, so
that their repetition may be avoided. In the following examples,
several elements according to the invention are represented in
combination with an example. Each of these elements according to
the invention can however also represent an advantageous embodiment
of the present invention independent of the other elements of the
respective example.
[0026] It is shown in
[0027] FIG. 1: A heat shield according to the state of the art;
[0028] FIG. 2: A heat shield according to the invention comprised
of two partial shells;
[0029] FIGS. 3 and 4: Top-views of heat shields according to the
invention;
[0030] FIGS. 5 to 7: Examples for the orientation of flow channels
according to the present invention;
[0031] FIG. 8: A heat shield according to the invention with a
hinge mechanism; and
[0032] FIG. 9: A further example for the orientation of flow
channels according to the present invention.
[0033] FIG. 1 shows a heat shield 1 with an outer metal layer 2. An
insulating layer 3 consisting in a porous material is arranged
essentially parallel to the metal sheet layer 2. The insulating
layer 3 is embedded into the metal layer 2 and reinforced by the
latter. The metal layer 2 consists in fire-aluminated stainless
steel, the insulating layer 3 in a glass-fiber mat free of binder.
The metal sheet layer 2 and the insulating layer 3 in their
geometry follow the geometry of the two adjoining parts and this
way show a three-dimensional form with convexities, e.g. in the
areas 40. The heat shield 1 according to FIG. 1 in practice is
combined with a second half-shell and corresponds to the state of
the art.
[0034] FIG. 2 schematically represents the construction of the heat
shield 1 from two half shells 1a and 1b in an exploded view. Both
the half shells are provided for encircling a catalyst 9 as the
adjacent part in a circular manner. The half shells themselves
consist in an aluminized, or stainless steel shell 2a, 2b, into
which an insulating layer 3a, 3b has been inserted each. Other than
the insulating layers in the state of the art, the insulating
layers 3a, 3b consist in a glass fiber mat which has been fixed
with a ceramic binder, so that the half shells keep their shape
permanently. This is especially required for the durable stability
of the channels 10, which pervade the insulating layer on its
surface pointing towards the part 9.
[0035] In FIG. 3, a half-shell of a heat shield 1 similar to the
one in FIG. 1 but according to the invention is shown in a top view
to the surface facing the hot part. As corresponds to the
invention, here on the surface of the heat shield 1 pointing
towards the hot part, grooves 10a to 10d are molded into the
insulation layer 3, through which gas can flow between the hot part
and the insulating layer 3. To this end, the grooves 10a to 10d
between their ends reach to the end of the insulating layer 3 and
therefore each comprise and inlet 5a to 5d and an outlet 6a to 6d.
The grooves 10a to 10d in the installed state continue in the
complementary half-shell that is not shown here. The grooves 10a to
10d show an essentially half-circular cross section, with a maximum
depth of the grooves of 8 mm and a maximum width of the grooves
being 10 mm.
[0036] In FIG. 4, a half-shell of a heat shield according to the
invention is shown in a top-view to the surface pointing towards
the hot part. Here, the insulating layer 3 is marked with an
undulating hatching. Again, the flow channels are molded as grooves
10a to 10g into the surface of the insulating layer, which faces
the hot part, the flow channels crossing the insulating layer up to
its edge. The edges 8 of the metallic layer 2 in several areas of
the border region towards the second half-shell protrude
collar-shaped to the outward and this way form a resting area for
corresponding collar-shaped protruding edges of the second
half-shell. The collar-shaped protruding edges to this end may
comprise passage openings for fastening means for the connection of
the two half-shells, these passage openings not being depicted in
detail here. As an alternative, the complementary edges can also be
fixed to each other by clamping or plugging connections.
[0037] FIG. 5 in partial figures A to D shows several possibilities
for the arrangement of the flow channels 10a to 10d on and within
the surface of an insulating layer 3. In FIG. 5A a total of four
flow channels 10 a to 10d which extend under an angle of about
120.degree. relative to the longitudinal axis of the hot part are
given. These channels surround the part and this way form a single
continuous channel. This follows from the corresponding
cross-sectional drawing in FIG. 5B, where the partial shells are
combined in a schematic drawing. FIG. 5B is a simplified drawing
which does not reflect that the channel sections 10a to 10d do not
extend in parallel to the plane of the paper, but as a helical
channel inclined to the latter, as follows from FIG. 5A.
Accordingly, the inlet and the outlet of the channel are situated
in front of and behind the plane of the paper.
[0038] FIG. 5C also shows channels 10a, 10b, 10c, and lad which
helically surround a hot part or to be more precise their sections,
here again, multi-layered helixes are given. Although the channels
10a to 10d extend in parallel to each other, the gases flowing in
channels 10a and 10c here flow in the opposite direction to the
gases flowing in channels 10b and 10d.
[0039] In FIG. 5D, an arrangement of two flow channels 10a and 10b,
which helically surround a hot part is shown. These are staggered
relative to each other, so that the convolutions of the two flow
channels 10a and 10b are extending in an alternatingly nested
manner. The two flow channels are arranged in such a way that their
passage is effected in a cross-flow.
[0040] In partial Figures A to C, FIG. 6 shows the arrangement of
flow channels in parallel to the longitudinal axes of a hot part.
FIG. 6A here shows a detail from the insulating layer 3, where four
flow channels 10a to 10d which are arranged in parallel to each
other and which extend in a straight way can be identified.
[0041] In FIG. 6B, a cross section through an arrangement of parts
is depicted which corresponds to the one in FIG. 6A. The channels
10a to 10d in their longitudinal direction, thus the direction
orthogonal to the drawing plane in FIG. 5B, extend in parallel to
each other. In FIG. 6B, one can realize that apart from channels
10a to 10d, further channels are given and that the heat shield 1
completely encircles the hot part 9 and this way insulates and
cools the latter.
[0042] In FIG. 6C, an arrangement of flow channels 10a to 10e is
shown, which to a large degree corresponds to the one in FIGS. 6A
and 6B, but where the channels 10a to 10e extend under an angle of
about 20.degree. to the longitudinal axis of the hot part 9, which
longitudinal axis extends horizontally in FIG. 6C.
[0043] In FIG. 7, too, a corresponding section of an insulating
layer 3 is shown, where the flow channels 10a to 10h extend under
an angle to the longitudinal axes of the hot part, which
longitudinal axis extends horizontally. In addition, the cross
section of the flow channels 10a to 10h compared to each other is
neither identical nor constant. In particular, the cross section of
the flow channels 10c to 10f is smaller than the one of channels
10a, 10b and 10g. Further, the distance of channels 10c to 10f to
each other is smaller and therefore, the density of channels in
this area is higher than for the channels 10a, 10b, 10g and 10h.
Such an arrangement and design of the flow channels can for
instance be chosen in the area of a hot spot of the hot part to be
shielded with the hot spot being covered by the channels 10c to
10f. With this, a better cool-down of the hot spot can be achieved,
as in the area of the hot spot, the flow velocity in the channels
10c to 10f is high and further, the density of the channels is
increased.
[0044] FIG. 8 illustrates a further embodiment of a heat shield
according to the invention. As in FIG. 2, the heat shield 1
consists in two half-shells 1a, 1b, which here are however
connected to each other via a hinge 7. The half-shells 10a, 10b, as
already described beforehand, each consist in an outer, metallic
layer 2a, 2b and an inner, insulating layer 3a, 3b. The ratio
between the thickness of the metal sheet layer 2a, 2b and of the
respective insulating layers, 3a and 3b are not to scale. In the
insulating layer 3a, 3b semi-circularly profiled channels 10a to
10d extend, which in a helical manner continue into or out of the
paper plane. When the two half-shells 1a, 1b of the heat shield 1
are closed around the part to be shielded 9 using the hinge 7, the
ends of the channels 10a, 10b in half-shell 1a find their
continuation in the other half-shell 1b which cannot be identified
here, and this way form a continuous helix. The protruding edges 8
of the two half-shells 2a, 2b upon closure at least in sections
come to rest in a facial way on each other and can be connected
using fasting means, e.g. clips or screws.
[0045] FIG. 9 shows a simplified cross section through an assembly
comprising a part to be shielded, and a heat shield arranged
immediately on this part, now in a further embodiment of the
invention. Here, the insulating layer 3 is not one-piece but
consists of three essentially concentrical layers 3, 3' 3'', which
in this order rest one on the other. Both the innermost layer 3 and
the outermost layer 3'' comprise flow channels for air, namely
channels 10a to 10d in the outermost layer 3''being delimited by
the metallic layer 2 and channels 10a' to 10 10d' in the innermost
layer delimited by the part 9. The way the simplified cross section
has been set up corresponds to the one used for FIG. 5B. Thus, it
is a simplified drawing which does not reflect that the channel
sections 10a to 10d and 10a' to 10d', respectively, do not extend
in parallel to the plane of the paper, but as helical channels
inclined to the latter. Accordingly, the inlet and the outlet of
the respective channels are situated in front of and behind the
plane of the paper. The arrows in FIG. 9 indicate that in the
innermost layer 3, the air in the channels 10a' to 10d' flow in the
clockwise direction when flowing from the spectator into the paper
plane, while the channels 10a to 10d in the outermost layer 3'' in
the same perspective flow in an anti-clockwise direction. This
allows for an influence of one channel to the other. If the air
flowing in the channels 10a to 10d in the outermost layer 3'' is
airflow, this allows for an extremely efficient cooling of the air
in the inner channels, without negative impact on the warm-up. As
an alternative to the inverse rotational sense of the two groups of
channels with the channels being shifted to each other shown here,
in the outermost and the innermost layer, an identical flow
direction and/or a parallel arrangement are possible as well. While
from a production perspective it is advantageous to design a heat
shield according to the invention with an insulating layer with
channels on its inner surface and its outer surface from several
layers of insulating material, it can be formed from a single
layer, too.
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