U.S. patent application number 10/510769 was filed with the patent office on 2005-08-11 for electric heating device, particularly for a heating or air-conditioning unit in a vehicle.
Invention is credited to Colette, Olivier, Marange, Christophe, Pierron, Frederic, Terranova, Gilbert.
Application Number | 20050175328 10/510769 |
Document ID | / |
Family ID | 28459763 |
Filed Date | 2005-08-11 |
United States Patent
Application |
20050175328 |
Kind Code |
A1 |
Pierron, Frederic ; et
al. |
August 11, 2005 |
Electric heating device, particularly for a heating or
air-conditioning unit in a vehicle
Abstract
Electric heating device comprising an electric radiator (10) for
heating the air passing through it, said radiator comprising a
casing (12), at least one resistive element mounted in the casing
and constituted by at least one zigzag metal strip (22) which is
disposed so as to be directly exposed to the air passing through
the casing, and a circuit (30) for controlling the electrical
supply of the resistive element or elements connected to a power
supply. The electric radiator (10) comprises a set of individual
heating modules (20) disposed parallel to one another in the casing
(12) and so as to be directly exposed to the air passing through
the casing, each heating module (20) comprising a pleated or
corrugated metal strip (22) and an electronic switch controlled by
the control circuit (30) intended to selectively inhibit the
electrical supply of the metal strip (22).
Inventors: |
Pierron, Frederic;
(Rambouillet, FR) ; Terranova, Gilbert; (Le Perray
en Yvelines, FR) ; Marange, Christophe; (Chatou,
FR) ; Colette, Olivier; (Le Mesnil Saint Denis,
FR) |
Correspondence
Address: |
Liniak Berenato
Longacre & White
Suite 240
6550 Rock Spring Drive
Bethesda
MD
20817
US
|
Family ID: |
28459763 |
Appl. No.: |
10/510769 |
Filed: |
October 12, 2004 |
PCT Filed: |
April 9, 2003 |
PCT NO: |
PCT/FR03/01125 |
Current U.S.
Class: |
392/347 ;
219/202 |
Current CPC
Class: |
F24H 9/1872 20130101;
H05B 3/16 20130101; F24H 3/0441 20130101; F24H 3/0435 20130101;
F24H 9/2071 20130101; F24H 3/0405 20130101; H05B 2203/02 20130101;
F24H 3/0429 20130101; F24H 3/0458 20130101; H05B 1/0236 20130101;
B60H 1/2225 20130101; F24H 3/0447 20130101 |
Class at
Publication: |
392/347 ;
219/202 |
International
Class: |
F24D 013/00; B60L
001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 11, 2002 |
FR |
02/04554 |
Claims
1. Electric heating device comprising an electric radiator (10) for
heating the air passing through it, said radiator comprising a
casing (12), at least one resistive element mounted in the casing
and constituted by at least one zigzag metal strip (22) which is
disposed so as to be directly exposed to the air passing through
the casing, and a circuit (30) for controlling the electrical
supply of the resistive element or elements connected to a power
supply, characterised in that the electric radiator (10) comprises
a set of individual heating modules (20) disposed parallel to one
another in the casing (12) and so as to be directly exposed to the
air passing through the casing, each heating module (20) comprising
a pleated or corrugated metal strip (22) and an electronic switch
(25) controlled by the control circuit (30) intended to selectively
inhibit the electrical supply of the metal strip (22).
2. Device according to claim 1, characterised in that each heating
module (20) also comprises an electrically insulating support (40)
comprising a moulded rail (45) intended to accommodate and hold in
position said metal strip (22).
3. Device according to claim 2, characterised in that the moulded
rail (45) has flanges (45a, 45b) between which the tops of the
corrugations are held laterally and separations (46) for
maintaining a certain regularity of the pitch of the corrugated or
pleated metal strip (22).
4. Device according to any one of claims 1 to 3, characterised in
that the heating module (20) comprises at least one thermal and
electrical protection element, directly exposed to the air passing
through the heating module and in series with the metal strip
(22).
5. Device according to claim 4, characterised in that the
protection element comprises at least one hot-melt link (58) in
series with a metal strip (22).
6. Device according to claim 4, characterised in that the
protection element comprises a spring blade (57) and a hot-melt
link (58) formed by a brazed joint between one end of the metal
strip (22) and one end of the spring blade (57), the other end of
the spring blade being immovably attached to the support (40) and
electrically connected to a terminal 56.
7. Device according to either one of claims 5 and 6, characterised
in that the brazed joint of the hot-melt link (58) has a melting
point matching an upper temperature limit.
8. Device according to claim 7, characterised in that the brazed
joint of the hot-melt link (58) is formed by a eutectic solder
joint.
9. Device according to claim 6, characterised in that the spring
blade (57) is directly exposed to the air passing through the
heating module (20) and openings in the form of louvres are formed
in the spring blade (57).
10. Device according to any one of claims 6 to 9, characterised in
that the spring blade (57) has a cross-section smaller than or
equal to that of the metal strip (22).
11. Device according to any one of claims 6 to 10, characterised in
that the spring blade (57) has a resistivity greater than or equal
to that of the metal strip (22).
12. Device according to any one of claims 1 to 11, characterised in
that a metal connection support (50) connected to the electrical
power supply is integrated into the insulating support (40)
allowing the electrical supply of the metal strip (22).
13. Device according to any one of claims 1 to 12, characterised in
that the electronic switch (25) is integrated onto the metal
connection support (50) through tracks formed by said support.
14. Device according to either one of claims 12 and 13,
characterised in that flanges (52) are formed in the metal
connection support (50) facilitating the heat dissipation of the
electronic switch (25) by the air passing through the heating
module (20).
15. Device according to any one of claims 6 to 14, characterised in
that the end of the spring blade (57) immovably attached to the
insulating support (40) is soldered permanently to the connection
terminal (56) electrically independent of the metal connection
support (50) thus allowing electrical connection of the strip or of
the spring blade to an external terminal or busbar (35).
16. Device according to any one of claims 1 to 15, characterised in
that each heating module (20) also comprises at least one
protection mechanism of reversible or resettable type (61)
connected directly or indirectly to the metal strip (22) preventing
excessive heating.
17. Device according to claim 16, characterised in that the
reversible protection mechanism (61) is a thermal sensor or
detector delivering information to the control circuit (30),
matching the temperature of the metal strip (22) or of the spring
blade (57) in order that the control circuit (30) disconnects the
electrical supply in the case of excessive heating.
18. Device according to claim 17, characterised in that the thermal
sensor or detector is connected thermally to the spring blade
(57).
19. Device according to either one of claims 17 and 18,
characterised in that the thermal sensor or detector comprises an
element chosen from amongst an NTC resistor, a PTC resistor, a
bimetallic strip and a PTC effect polymer switch.
20. Device according to any one of claims 6 to 18, characterised in
that moreover the spring blade (57) has a PTC effect thus providing
the function of a thermal sensor.
21. Device according to any one of claims 1 to 20, characterised in
that each heating module (20) has a heating power of between 0 and
500 W and preferably between 300 W and 400 W.
22. Device according to any one of claims 1 to 21, characterised in
that the casing (12) comprises a set of cells (14) intended to
accommodate and hold in place each heating module (20).
23. Device according to claim 22, characterised in that the casing
(12) receives a cover (39).
24. Device according to any one of claims 1 to 23, characterised in
that the control circuit (30) comprises means of varying the power
supplied by the radiator by modulating the supply voltage delivered
to each heating module (20).
25. Device according to claim 24, characterised in that the control
circuit (30) comprises means of varying the supplied power by pulse
width modulation.
26. Device according to any one of claims 1 to 25, characterised in
that the different heating modules (20) comprise metal strips (22)
having substantially identical resistances.
27. Device according to any one of claims 1 to 26, characterised in
that each metal strip (22) of each heating module (20) has a
corrugation period with a length of between 1.8 mm and 6 mm.
28. Device according to any one of claims 1 to 27, characterised in
that each metal strip (22) of each heating module has a
peak-to-peak amplitude between corrugation tops of between 5 mm and
20 mm.
29. Device according to any one of claims 1 to 28, characterised in
that each metal strip (22) of each heating module has a width of
between 5 mm and 20 mm.
30. Device according to any one of claims 1 to 29, characterised in
that each metal strip (22) of each heating module has a thickness
of between 50 .mu.m and 250 .mu.m and preferably between 80 .mu.m
and 180 .mu.m.
31. Device according to any one of claims 1 to 30, characterised in
that each metal strip (22) of each heating module is made of a
material chosen from amongst an iron-based alloy and a copper-based
alloy.
32. Device according to claim 31, characterised in that the
copper-based alloy is an alloy chosen from amongst CuNi30, CuNi45
and CuNi18Zn20.
33. Device according to claim 31, characterised in that the
material is an alloy having a positive temperature coefficient
resistance effect.
34. Device according to any one of claims 1 to 33, characterised in
that openings in the form of louvres (26) are formed in each strip
(22).
35. Device according to claim 34, characterised in that the louvres
(26) comprise fins (26a) which form an angle of between 200 and 350
with respect to the plane of the strip (22).
36. Device according to any one of claims 1 to 35, characterised in
that each strip (22) is provided with an electrically insulating
and/or corrosion protection covering.
37. Device according to any one of claims 1 to 35, characterised in
that each metal strip (22) has a profile chosen from amongst a
sinusoidal profile, a triangular profile, a rectangular profile and
a trapezoidal profile.
38. Device according to any one of claims 1 to 37, also comprising
an air flow generator (7), characterised in that the electronic
switches (25) driven by the control circuit (30) inhibit the
electrical supply of the heating modules (20) when the air flow
rate passing through the radiator (10) is below a minimum value, in
order to provide protection against excessive heating.
39. Device according to claim 38, in which the air flow generator
(7) comprises a fan (3), characterised in that means are provided
for supplying the control circuit (30) with a signal representing
the speed of rotation of the fan in order to inhibit the electrical
supply of the heating modules when the speed of rotation of the fan
is below a predetermined threshold.
40. Heating or air-conditioning apparatus for a motor vehicle,
characterised in that it comprises a heating device according to
any one of claims 1 to 39.
41. Apparatus according to claim 40, characterised in that it
comprises an electric radiator disposed downstream of a liquid heat
exchanger in an air circulation channel.
42. Apparatus according to either one of claims 40 and 41,
characterised in that the electric radiator is disposed in
proximity to an air outlet aperture.
Description
BACKGROUND OF THE INVENTION
[0001] The invention concerns an electric heating device comprising
an electric radiator passed through by the air to be heated and in
particular passed through by at least part of an air flow produced
by an air flow generator, such as a fan or blower.
[0002] The field of application of the invention is more
particularly that of heating and/or air-conditioning apparatuses
for vehicles, in particular private and commercial motor vehicles
and heavy lorries.
[0003] Usually, the heating up of the air intended for heating the
passenger compartment of a motor vehicle, and for demisting and
defrosting, is provided by passing a flow of air through a heat
exchanger through which the engine block cooling liquid runs.
[0004] This heating method may prove unsuitable or insufficient in
a number of situations such as:
[0005] preconditioning before starting the engine in order to
provide heating up of the passenger compartment, and defrosting or
demisting, in a remote or pre-programmed manner, before use of the
vehicle in a very cold environment,
[0006] desired very fast rise in temperature in the passenger
compartment,
[0007] inability of the heat exchanger to supply the calories
necessary for satisfactory heating up of the air in order to
provide the heating functions and possible defrosting and demisting
functions, as occurs during a certain time after starting, with
certain types of engine with low heat loss.
[0008] To overcome these drawbacks, a known solution, among others,
consists of adding to the heat exchanger an electric radiator
disposed downstream of the exchanger in the circulation duct for
the air to be heated up. The operation of the electric radiator is
controlled on a temporary basis, until the heat exchanger on its
own can provide the heating of the air in the required manner.
[0009] Usually, such a supplementary electric radiator uses
resistive elements in the form of positive temperature coefficient
(PTC) resistors. The use of PTC resistors in fact allows
temperature self-limiting so that excessive heating is avoided. The
PTC resistors are in the form of small blocks or "jewels", disposed
in heating bars, between two electrodes. Radiant elements are
associated with the bars in order to facilitate heat exchange with
the air flow passing through the radiator. These radiant elements
can be fins through which the bars pass or else inserts for example
in the form of pleated or corrugated metal strips disposed between
parallel bars.
[0010] The additional PTC resistor electric radiators work
satisfactorily but have the drawback of having a high production
cost owing to the cost of the PTC resistors, the number of
constituent components, the necessary assembly time and the
sensitivity to corrosion of the supply electrodes of the PTC
resistors.
OBJECT AND SUMMARY OF THE INVENTION
[0011] The aim of the invention is to provide an electric radiator
for a vehicle heating or air-conditioning apparatus or, more
generally, for an apparatus for heating any type of passenger
compartment which has a competitive cost compared with that of PTC
resistor electric radiators and which has a simplified architecture
in comparison therewith whilst allowing optimisation of the thermal
exchanges with air to be heated up.
[0012] Another aim of the present invention is to limit the number
of components of the radiator, thus facilitating its mounting and
reducing the manufacturing costs.
[0013] These aims are achieved by means of a heating device which
comprises an electric radiator for heating the air passing through
it, said radiator comprising a casing, at least one resistive
element mounted in the casing and constituted by at least one
zigzag metal strip which is disposed so as to be directly exposed
to the air passing through the casing, and a circuit for
controlling the electrical supply of the resistive element or
elements connected to a power supply, characterised in that the
electric radiator comprises a set of individual heating modules
disposed parallel to one another in the casing and so as to be
directly exposed to the air passing through the casing, each
heating module comprising a pleated or corrugated metal strip and
an electronic switch controlled by the control circuit intended to
selectively inhibit the electrical supply of the metal strip.
[0014] Each heating module also comprises an electrically
insulating support comprising a moulded rail intended to
accommodate and hold in position said metal strip.
[0015] Advantageously, the moulded rail has flanges between which
the tops of the corrugations are held laterally and separations for
maintaining a certain regularity of the pitch of the corrugated or
pleated metal strip.
[0016] Each heating module comprises at least one thermal and
electrical protection element, directly exposed to the air passing
through the heating module and in series with the metal strip.
[0017] The protection element comprises at least one hot-melt link
in series with a metal strip.
[0018] Preferably, the protection element comprises a spring blade
and a hot-melt link formed by a brazed joint between one end of the
metal strip and one end of the spring blade, the other end of the
spring blade being immovably attached to the support and
electrically connected to a terminal.
[0019] The brazed joint of the hot-melt link has a melting point
matching an upper temperature limit and can be formed by a eutectic
solder joint.
[0020] Advantageously, the spring blade is directly exposed to the
air passing through the heating module and openings in the form of
louvres are formed in the spring blade.
[0021] The spring blade has a cross-section smaller than or equal
to and a resistivity greater than or equal to that of the metal
strip.
[0022] According to a preferred embodiment, a metal connection
support connected to the electrical power supply is integrated into
the insulating support allowing the electrical supply of the metal
strip.
[0023] The electronic switch is integrated onto the metal
connection support through tracks formed by said metal support and
flanges are formed in the metal support facilitating the heat
dissipation of the electronic switch by the air passing through the
heating module.
[0024] The end of the spring blade immovably attached to the
support can be soldered permanently to the connection terminal,
electrically independent of the metal connection support, thus
allowing electrical connection of the strip or of the spring blade
to an external terminal or busbar.
[0025] Preferably, each heating module also comprises at least one
protection mechanism of reversible or resettable type connected
directly or indirectly to the metal strip preventing excessive
heating. This protection mechanism can be a thermal sensor or
detector delivering information to the control circuit, matching
the temperature of the metal strip or of the spring blade in order
that the control circuit disconnects the electrical supply in the
case of excessive heating.
[0026] The thermal sensor or detector is connected thermally to the
spring blade and comprises an element chosen from amongst an NTC
resistor, a PTC resistor, a bimetallic strip and a PTC effect
polymer switch.
[0027] Advantageously, the spring blade has a PTC effect thus
providing the function of a thermal sensor.
[0028] Each heating module can have a heating power of between 0
and 500 W and preferably between 300 W and 400 W.
[0029] The casing comprises a set of cells intended to accommodate
and hold in place each heating module by means also of a cover.
[0030] The control circuit can comprise means of varying the power
supplied by the radiator by modulating the supply voltage delivered
to each heating module, for example by the pulse width modulation
technique, which makes it possible to vary the power continuously
or almost continuously.
[0031] Advantageously, the different heating modules comprise metal
strips having substantially identical resistances.
[0032] Preferably, each metal strip of each heating module has a
corrugation pitch with a length of between 1.8 mm and 6 mm; a
peak-to-peak amplitude between corrugation tops of between 5 mm and
20 mm; a width of between 5 mm and 20 mm; and a thickness of
between 50 .mu.m and 250 .mu.m and preferably between 80 .mu.m and
180 .mu.m.
[0033] Each metal strip is made of a material chosen from amongst
an iron-based alloy and a copper-based alloy.
[0034] Preferably also, the copper-based alloy is an alloy chosen
from amongst CuNi30, CuNi45 and CuNi18Zn20.
[0035] Advantageously, the material is an alloy having a positive
temperature coefficient resistance effect.
[0036] According to a preferred embodiment, openings in the form of
louvres are formed in each strip. The louvres comprise fins which
form an angle of between 20.degree. and 35.degree. with respect to
the plane of the strip.
[0037] Advantageously, each strip is provided with an electrically
insulating and/or corrosion protection covering.
[0038] Each metal strip has a profile chosen from amongst a
sinusoidal profile, a triangular profile, a rectangular profile and
a trapezoidal profile. According to a preferred embodiment, the
heating device also comprises an air flow generator, characterised
in that the electrical switches driven by the control circuit
inhibit the electrical supply of the heating modules when the air
flow rate passing through the radiator is below a minimum value, in
order to provide protection against excessive heating.
[0039] According to a particular feature of the heating device, the
air flow generator comprises a fan, characterised in that means are
provided for supplying the control circuit with a signal
representing the speed of rotation of the fan in order to inhibit
the electrical supply of the heating modules when the speed of
rotation of the fan is below a predetermined threshold.
[0040] Another object of the invention is a motor vehicle heating
or air-conditioning apparatus using a heating device as defined
above.
[0041] In such a heating or air-conditioning apparatus, the
radiator of the heating device can be disposed in an air
circulation channel downstream of a possible liquid heat
exchanger.
[0042] According to a particular feature of the heating or
air-conditioning apparatus, the electric radiator can be housed in
proximity to an air outlet aperture.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] The invention will be better understood from a reading of
the description given hereinafter, on an indicative but
non-limiting basis, with reference to the accompanying drawings, in
which:
[0044] FIG. 1 is a highly schematic partial view of a heating
apparatus for a motor vehicle;
[0045] FIGS. 2 and 3 are perspective views of one embodiment of an
electric radiator for a heating device according to the
invention;
[0046] FIGS. 4 and 5 are perspective views of a heating module of
the radiator of FIGS. 2 and 3;
[0047] FIG. 6 is a partial detail view of a moulded rail of the
heating module of FIGS. 4 and 5;
[0048] FIG. 7 is a partial plan view of the electric radiator of
FIGS. 2 and 3;
[0049] FIGS. 8 and 9 are partial detail views showing variant
implementations of a hot-melt link for protecting the radiator
against excessive heating;
[0050] FIG. 10 is a partial detail view showing a reversible
protection mechanism in addition to the hot-melt protection link of
FIG. 8;
[0051] FIG. 11 is a perspective view of a casing of an electric
radiator of FIGS. 2 and 3;
[0052] FIGS. 12 and 13 are partial detail views showing the
positioning of a heating module of the radiator of FIGS. 2 and
3;
[0053] FIG. 14 is a partial plan view, on an enlarged scale, of a
metal strip with louvre for a heating module of FIGS. 4 and 5 (in
the non-pleated state);
[0054] FIG. 15 is a sectional view along the plane XV-XV of FIG.
14;
[0055] FIG. 16 is an embodiment of an electrical diagram of a
radiator of a heating device according to the invention; and
[0056] FIG. 17 illustrates highly schematically another embodiment
of a heating and/or air-conditioning apparatus using a heating
device according to the invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0057] FIG. 1 shows part of a motor vehicle heating apparatus,
comprising a casing 2 delimiting a channel 3 for the passage of air
to be heated up. The channel 3 conveys the air to heating and
demisting/defrosting apertures in order to be selectively
distributed in the passenger compartment according to the positions
of mixing and distribution flaps 6. The air flow rate in the
channel 3 is produced by a blower 7, or fan, receiving external air
or recirculation air coming from the passenger compartment. The
heating up of the air, when necessary, is provided by a possible
liquid heat exchanger 8, using the cooling liquid of the engine as
a heat-conducting liquid, and by an electric radiator 10. The
exchanger 8 and the electric radiator 10 are disposed in the
channel 3, the first being situated upstream of the second. In the
absence of the exchanger 8, the heating of the air is provided by
the electric radiator 10 alone.
[0058] The electric radiator 10 can occupy all or part of the
passage cross-section of the channel 3. In the latter case, only
part of the air flow produced by the fan 7 passes through the
electric radiator, the other part being diverted outside
thereof.
[0059] One method of mounting an electric radiator in a heating and
air-conditioning apparatus is described in particular in the French
patent application 01 09 076 of the applicant.
[0060] One example implementation of an electric radiator 10 in
accordance with the invention will now be described with reference
to FIGS. 2 to 15.
[0061] As shown in FIGS. 2 and 3, the electric radiator 10
comprises a casing 12, for example made of plastic, in which there
is housed a set of individual heating modules 20. The individual
heating modules 20 are disposed parallel to one another and extend
over the entire length of the casing 12, so as to be directly
exposed to the air passing through this casing.
[0062] The control of the electric radiator 10 is provided by a
control circuit 30 mounted on a printed circuit board 31
advantageously housed in one of the sides of the casing 12 and
protected by a cap 33.
[0063] The control circuit 30 receives information through a
connector 37 and is connected to a power supply through busbars 35
or through the connector.
[0064] As shown in FIGS. 4 and 5, each individual heating module 20
comprises a metal strip 22, preferably pleated or corrugated, and
an electronic switch or change-over switch 25, for example in the
form of a power transistor. The electronic switch 25 is controlled
by the control circuit 30 in order to selectively inhibit the
electrical supply of the metal strip 22.
[0065] Advantageously, the different heating modules comprise metal
strips 22 having substantially identical resistances and a heating
power of between 0 and 500 W and preferably between 300 W and 400
W.
[0066] The individual heating module 20 comprises an electrically
insulating support 40 comprising a rigid moulded rail 45 intended
to accommodate and hold in position an identical continuous
strip.
[0067] The moulded rail 45, as shown in FIG. 6, has an H-shaped
cross-section and has flanges 45a, 45b between which the tops of
the corrugations are held laterally. Thus, the continuous strip is
disposed in two rows, winding around the lateral sides of the
moulded rail 45. The strip 22 is turned back or curved at one end
of the moulded rail 45. In a variant, the strip can be in two
segments soldered to the end of the moulded rail 45.
[0068] The moulded rail 45 incorporates separations 46 making it
possible to clamp the strip 22 and maintain a certain regularity of
the corrugation pitch of the strip.
[0069] Thus, the insulating support 40 participates in the holding,
guidance and anchorage of the metal strip 22 mechanically.
[0070] However, the strip 22 can be fixed to the moulded rail 45 by
gluing of corrugation tops on this moulded rail in order to limit
noise-generating vibrations.
[0071] The electrical supply of the strip is carried out via a
metal electrically conductive connection support 50, for example
made of copper or one of its alloys. The metal connection support
50 is integrated into the insulating support 40 by overmoulding or
by other known methods.
[0072] The electronic switch 25 is integrated on the metal
connection support 50 through tracks, not depicted, formed by this
metal support.
[0073] Moreover, dissipating flanges 52 and connection terminals 54
are cut out of the metal support 50. The dissipating flanges 52
facilitate the dissipation of heat of the electronic switch by the
air passing through the individual heating module 20, whilst the
connection terminals 54 connect this individual heating module to
the control circuit 30.
[0074] Protection of the radiator against excessive heating is
provided by the control circuit 30 and the electronic switches 25
as will be explained later. However, for the sake of maximum
safety, additional protection against excessive heating of the
radiator is provided by means of at least one thermal and
electrical protection element in each individual heating module.
This protection element must be in series with the metal strip and
preferably must be directly exposed to the air passing through the
heating module.
[0075] FIGS. 7 and 8 show an example of a protection element
consisting of a spring blade 57 and a hot-melt link 58 formed by a
brazed joint between one end of the metal strip 22 and one end of
the spring blade 57. The other end of the spring blade 57 is fixed,
for example by a permanent weld, to a connection terminal 56 which
is immovably attached to the support 40 of the metal strip 22. The
connection terminal 56 connects the strip 22 to a busbar 35 and is
electrically independent of the metal connection support 50.
[0076] The brazed joint composition used for the electrical link is
chosen so that this brazed joint has a precise melting point at a
temperature representing an upper permissible temperature limit.
This limit is fixed so that the protection by opening of the
hot-melt link is the one which acts last. By way of example, the
hot-melt link 58 can be formed by a eutectic solder joint such that
its melting temperature is approximately 165.degree. C.
[0077] This is because this protection aims to protect the plastic
components of the electric radiator from any deformation or
combustion. It is a final protection and is active in the case of a
failure of the electronics due for example to a short circuit.
[0078] On account of the elastic prestressing exerted on the spring
blade 57, the melting of the hot-melt link allows a relaxation of
the spring blade 57 and therefore a definite opening of the
link.
[0079] Being directly exposed to the air passing through the
radiator, the spring blade 57 participates in part in the heating
of the air.
[0080] Moreover, the spring blade 57 has a cross-section less than
or equal to and a resistivity greater than or equal to that of the
metal strip 22. Consequently, the density of the current through
the spring blade 57 is greater than that passing through the strip
22 and therefore the spring blade 57 heats up more quickly than the
strip 22.
[0081] In other words, the thermal gradient of the spring blade 57
is greater than that of the strip 22 and therefore the blade is
more sensitive to temperature changes.
[0082] In the vicinity of the hot-melt link, the spring blade 57
has a temperature greater than that of the strip 22 thus
compensating for any temperature difference all along the strip
22.
[0083] The constituent material of the spring blade as well as its
shape and size are chosen according to the electrical and thermal
conductivity necessary for meeting optimum protection.
[0084] The material can be chosen from amongst metals with a high
electrical resistivity, like a copper alloy, such as for example
CuNi30. The spring blade can have a width of approximately 10 mm, a
thickness of approximately 100 .mu.m, a length of between 15 mm and
30 mm and a resistance less than or equal to 10 m.OMEGA..
[0085] Moreover, openings (not depicted) in the form of louvres can
be formed in the spring blade thus increasing its thermal
sensitivity in the case of low air flow rate.
[0086] The result of all these characteristics is that the
protection element reacts fairly quickly to any excessive heating
of the radiator for different air flow rates through the radiator.
The protection is valid at the time of a progressive lowering of
the air flow or at the time of a sudden cutoff of the air flow.
[0087] Moreover, the protection element of FIG. 8 can act as a fuse
in the case of short-circuiting of the metal strip with an external
electrical potential.
[0088] FIG. 9 shows that a hot-melt link 58 can also be formed by
cutting up a strip 22 and connecting its sections by brazing by
means of an adapted brazed joint.
[0089] FIG. 10 shows that use can be made of a reversible or
resettable protection mechanism, connected directly or indirectly
to each metal strip, against excessive heating defined by a
temperature below that corresponding to the melting point of the
hot-melt link.
[0090] This reversible protection mechanism can consist of a
thermal sensor or detector delivering information to the control
circuit, matching the temperature of the metal strip or of the
spring blade, in order that the control circuit disconnects the
electrical supply in the case of excessive heating.
[0091] Preferably, the thermal sensor or detector 61 is thermally
connected, for example by a thermal adhesive 63 or resin, to the
spring blade 57.
[0092] The thermal sensor or detector can be of a type known per
se, such as a bimetallic strip having an adapted opening threshold,
a PTC resistor, an NTC resistor or a PTC effect polymer switch
connected directly or indirectly to the metal strip.
[0093] Advantageously, the spring blade can have a PTC effect thus
providing the function of a thermal sensor.
[0094] FIGS. 11 to 13, in addition to FIGS. 2 to 6, show the
mounting of the individual heating modules 20 in the casing 12.
[0095] In effect, the casing is rectangular comprising longitudinal
walls 13 which define between them a set of cells 14. By way of
example, FIG. 11 shows three cells, intended to accommodate and
hold in place three individual heating modules 20. Of course, this
number is in no way limiting and can be different.
[0096] Each heating module 20 is clamped in the cell 13 of the
casing 12 via the edges or tops of the metal strip 22 against the
longitudinal walls 13.
[0097] On one transverse side of the casing 12, each longitudinal
wall 13 ends with a transverse return or shoulder 15 which fits in
a corresponding slot 23 formed on one end of each support 40 of the
individual heating module 20. This provides polarisation and
correct positioning of the individual heating module 20 and its
components, in particular the electronic switch. Similarly, at the
same transverse side, notches 19 are formed for adjusting the
positioning of the individual heating modules 20.
[0098] The opposite transverse side comprises slots 16 intended to
accommodate the ends of the moulded rails 45 of the individual
heating modules 20.
[0099] Moreover, the casing can comprise central cross members for
rigidifying the casing and better supporting the individual heating
modules 20.
[0100] A cover 39 comprising openings of the same shapes and
dimensions as the cells 14 plugs on the casing 12. In fact, the
external longitudinal walls of the casing 12 comprise recesses 18
intended to accommodate clips or clasps 71 formed in the cover
39.
[0101] The internal face of the cover 39 comprises a system for
clamping and positioning the heating modules, identical or
symmetrical to that of the casing, as shown in FIG. 13.
[0102] The casing 12 and the cover delimit, by means of their cells
and corresponding openings, the cross-section of passage of the air
through the metal strips 22 and electronic switches 25. Thus, the
air flow is heated by the strips whilst cooling the electronic
switches.
[0103] The casing 12, the cover 39, the cap 33 and the moulded
rails 45 of the heating modules 20 are produced from an
electrically insulating material, for example a plastic material
capable of withstanding the maximum temperature reached in service,
that is to say a temperature which may go up to 150.degree. C.
Plastic materials which can be used are for example PBT, PPS, PPA,
PA66 and PA6, possibly reinforced with glass fibres. The casing 12
can be moulded in a single piece.
[0104] The busbars 35 are fixed in the casing 12 by rivet heading
or can be crimped or clipped on the cover 39 and the casing 12. In
a variant, the busbars 35 can be integrated in the casing by
overmoulding.
[0105] The busbars 35 can be threaded in order to fix power
terminals 73 of the electrical supply by a system of nuts 41.
[0106] Furthermore, the electric radiator comprises fixing and
guidance means 61 in order to facilitate its mounting and
integration in a heating and air-conditioning apparatus.
[0107] Moreover, the electric radiator comprises a sealing bead in
order to limit air leakages between the channel which conveys the
air to be heated and the external environment.
[0108] The metal strips 22 have their main faces disposed
substantially parallel to the direction of flowing of the air flow
through the casing 12, so as to limit the pressure loss due to the
passage of the air in the electric radiator. In order to increase
the thermal exchange between the strips and the air flow to which
they are directly exposed, louvres 26 (shown only in FIGS. 14 and
15) can possibly be formed in the strips. The louvres 26 are
produced by cutting out fins 26a and deforming these slightly
outside the plane of the strips.
[0109] The louvres make it possible to increase the efficiency of
the thermal exchange by virtue of the turbulence created at the
cells of the fins 26a. The angle between the fins and the plane of
the strip is preferably between 20.degree. and 35.degree. in order
to obtain a good compromise between the sought effectiveness of the
fins and the pressure loss they lead to by increasing the air
resistance.
[0110] The strips 22 are preferably covered with a layer having an
electrical insulation function, for example an insulating varnish
or a resin such as an epoxy resin, possibly also capable of having
a corrosion protection function.
[0111] The constituent material of the strips 22 as well as their
shapes and dimensions are chosen according to a number of
constraints or characteristics such as the electrical resistance
necessary for satisfying the power requirements, the resistivity,
feasibility, geometrical parameters of the electric radiator,
etc.
[0112] The material can be chosen from amongst metals with a high
electrical resistivity which are capable of being put in the form
of ribbons from which bands can be cut out and pleated in order to
form the strips 22. Such metals are in particular iron- or
copper-based alloys containing in particular nickel and/or tin.
Preferably, the material of the strips consists of CuNi30, CuNi45
or CuNi18Zn20. Advantageously, these alloys can have a positive
temperature coefficient resistance effect.
[0113] The metal strips can have sinusoidal, triangular,
rectangular or trapezoidal shapes.
[0114] The shapes and dimensions of a strip 22 can be dictated by
various considerations.
[0115] The thickness of the strip must be sufficient to allow the
industrial working of the metal ribbon, but remain limited in order
to not create too high an air resistance. A thickness value of
between approximately 50 .mu.m and 250 .mu.m is preferred.
[0116] The corrugation pitch or period of a pleated strip must not
be too small at the risk of creating too high an air resistance. On
the other hand, beyond a certain value, too great a pitch
prejudices the thermal exchange surface without providing any
substantial advantage in terms of reduction of air resistance, that
is to say reduction of pressure loss between the two faces of the
radiator. A pitch value of between approximately 1.8 mm and 6 mm is
preferred.
[0117] The width and the peak-to-peak height or amplitude between
corrugations depend on the space available for the electric
radiator. Furthermore, the width of the strip must be sufficient to
provide mechanical strength of the strip but remain limited to
avoid too large a space requirement. A width value of between
approximately 5 mm and 20 mm is preferred.
[0118] The height must not be too small in order to not contribute
towards a high air resistance. On the other hand, this height must
be limited in order to retain rigidity and sufficient strength of
the strip. A height value h of between approximately 5 mm and 20 mm
is preferred.
[0119] The length of a pleated strip, that is to say the length of
the moulded rail, depends on the space available for the electric
radiator. In a motor vehicle heating apparatus, this length is
usually from one to a few tens of centimetres.
[0120] Thus, the basic architecture of the electric radiator is
formed by the association of a set of individual heating modules
and standards. This is because each heating module comprises all
the functions allowing it to be independent of the other modules,
that is to say it comprises a strip, a strip support, an electronic
switch and at least one thermal protection element. Moreover, the
electronic power part of the modules is separate from the control
electronics, thus making it possible to standardise the heating
modules.
[0121] FIG. 16 is an electrical diagram of the radiator
illustrating a control circuit 30, electronic switches 25a, 25b,
25c and metal strips 22a, 22b, 22c according to the invention.
[0122] The control circuit 30 receives through the connector 37 an
item of information, for example of logic type, transported by a
data bus 60 and representing the required heating power level P.
The circuit 30 is also connected to an energy bus formed from a
conductor 62a at electrical network potential +Vr available in the
vehicle, for example the battery voltage, and a conductor 62b taken
to the reference potential (earth). In a variant, the circuit 30
can be supplied with energy via the connector 37 and in that case
its connection with the conductor 62a can be omitted.
[0123] In the example of FIG. 16, there are three strips. One
terminal of each strip is connected to the conductor 62b via its
corresponding switch whilst the other terminal of each strip is
connected to the conductor 62a via the hot-melt link 58 and the
spring blade 57. In addition, a thermal detector 61, connected to
the control circuit, is mounted at the level of each spring blade
57. Thus, each thermal detector delivers an item of information to
the control circuit, matching the temperature of the associated
spring blade.
[0124] In the case of excessive heating due to insufficient removal
of the calories produced, for example when the air flow rate
passing through a heating module is below a minimum value, the
corresponding electronic switch, driven by the control circuit 30,
inhibits the electrical supply of the heating module.
[0125] Furthermore, in a known manner, a signal representing the
speed of rotation of the fan can be sent to the control circuit 30
in order to inhibit the electrical supply of the individual heating
modules when the speed of rotation of the fan is below a
predetermined threshold.
[0126] It is possible to vary the power continuously or almost
continuously by modulating the electrical supply voltage of the
metal strips, or at least of one of them. The modulation can be
carried out in a known manner by pulse width modulation (PWM), the
voltage Vr being chopped in order to be delivered to the metal
strips in the form of a pulse train in which the ratio between
width and period of the pulses is variable. Modulated simultaneous
supplying of all the metal strips makes it possible, irrespective
of the power level P, to uniformly distribute the heat emission in
the entire cross-section of passage of the air in the electric
radiator.
[0127] The electric heating device according to the invention can
be used in heating and/or air-conditioning apparatuses other than
those of FIG. 1.
[0128] Thus, FIG. 17 shows a heating and/or air-conditioning
apparatus for a motor vehicle which is distinguished from that of
FIG. 1 in that the radiator 10 is not situated in proximity to the
heat exchanger 8, but in the immediate vicinity of an output of the
heating apparatus connected by a duct 4 to a demisting/defrosting
aperture 4a. A radiator in accordance with the invention could also
be mounted in the vicinity of the demisting/defrosting aperture 4a,
as shown by the reference 10', or in the vicinity of a heating
aperture 5a of the passenger compartment connected to the channel 3
by a duct 5 as shown by the reference 10".
[0129] Moreover, FIG. 17 shows that a radiator 10 in accordance
with the invention can be integrated in a motor vehicle
air-conditioning device comprising in the channel 3 a cooling
circuit evaporator 9, upstream of the heat exchanger 8, occupying
in this example only part of the cross-section of the channel.
* * * * *