US20070029253A1

US20070029253A1 - Electrical heating module for air flow heating, in particular for heating and ventilation of seats

Info

Publication number: US20070029253A1
Application number: US11/462,094
Authority: US
Inventors: Ingo Schehr
Original assignee: Microhellix Systems GmbH
Current assignee: MicroHellix GmbH
Priority date: 2005-08-06
Filing date: 2006-08-03
Publication date: 2007-02-08
Also published as: EP1783439A2; EP1772684A2; JP2007046894A; EP1783439B1; DE202005012394U1; EP1783439A3; US20070045262A1; US7560663B2; JP2007046893A

Abstract

An electric heating module for heating an air flow, in particular for heating and ventilating seats is provided, having at least one PTC-heating element 8 and at least one heat dissipation area 2 adjacent thereto that allows air to flow therethrough, having heat-conducting ribs 1, which are in an effective connection to the PTC-heating element 8 and combined therewith to form a module. The heat-conducting ribs 1 are formed from strips, which are combined in the area of the PTC-heating element 8 to form at least one packet of strips 3 formed by ribs 1 being in a heat-conducting contact to one another, while they are fanned out in the heat dissipation area 2.

Description

BACKGROUND

The invention relates to an electrical heating module for heating air flow according to the preamble of claim 1. This heating module is particularly used for heating and ventilation of seats. It comprises essentially at least one PTC-heating element and at least one heat dissipation area adjacent thereto having heat-conducting ribs, through which air can flow, effectively connected to the PTC-heating element and combined with them to form a single module.
PTC-elements are semi-conductor resistors made from ceramics, with their active resistance varying depending on temperature. The characteristic resistance-temperature line does not progress linearly: the resistance of a PTC-heating element initially reduces slightly with an increasing temperature of the component in order to, then, rise very rapidly at a characteristic temperature (reference temperature). This overall positive progression of the characteristic resistance-temperature line (PTC=positive temperature coefficient) leads to a PTC-heating element having self-adjusting features. At a component temperature distinctly lower than the reference temperature the PTC-heating element has a lower resistance so that appropriately high current can be conducted through it. When a good heat dissipation from the surface of the PTC-heating element is ensured, an appropriately high electric charge is accepted and released in the form of heat. However, when the temperature of the PTC-heating element exceeds the reference temperature, the PTC-resistance increases rapidly so that the electric power draw is limited to a very low value. The temperature of the component then approaches an upper limit, which depends on the heat absorption of the environment of the PTC-heating element. Under normal environmental conditions, the temperature of the component of the PTC-heating element can therefore not exceed a characteristic maximum temperature, even when the intended heat dissipation is entirely interrupted in a malfunction. This fact and the self-adjusting features of a PTC-heating element, based on which the drawn electric power is precisely equivalent to the thermal power dissipated, predestines PTC-heating elements for the use in heating and/or air conditioning arrangements of vehicles or in other applications of air flow heating in vehicles. For safety reasons, in this application field even in the case of a malfunction no flammable temperatures may develop in the heating element, although in normal operation high heating output is required.
In order to heat the interior compartment of motor vehicles it has been known to use electric heating modules having a frame, which forms a module by combining a multitude of PTC-heating elements and adjacent heat dissipating areas, through which air can flow, having heat-conducting ribs. An example for such electric heating modules known is found in EP 0 350 528 A1.
In EP b 1 479 918 A1 a complete fan module, comprising a radial fan integrated in a housing and a heating module of the type mentioned at the outset, is disclosed serving to heat the seat in a ventilated vehicle seat. Due to the fact that, for safety reasons, a vehicle seat may not exceed a maximum temperature at its surface, suitable for human beings, heating modules with PTC-heating elements are excellently suitable, even in case of a ventilator malfunction, because, while they provide the same level of safety, they can release a considerably higher heating power than mats conventionally used in heated seats with electric resistance wires, whose power draw is very limited for safety reasons.
The previously known electric modules of the type mentioned at the outset generally comprise several layers of planar PTC-heating elements, arranged side-by-side, with their narrow sides being in the line of the air flow, with their flat upper sides and their lower sides each electrically contacting contact metal sheets. The heat dissipation areas adjacent thereto are provided with meandering metal ribs, which are also located with their narrow sides in line with the air flow and thermally contact, supported at their broad side, the contacting metal sheets of the PTC-heating elements in regular intervals for heat transfer. In order to achieve a good heat transfer from the PTC-heating elements to the heat conducting ribs, a heat conducting glue or other connection techniques can be used; however, a more efficient solution has become widely accepted, i.e. to insert the PTC-heating elements and the heat conducting bars into a frame, combining them into a module, and to provide at least one spring element in the frame, which presses the alternating arranged heat dissipation areas with the heat conducting bars and the bars with the PTC-heating elements against one another.
However, this requires a rectangular shape of the electric heating module with cellular structures of the components, which is not the best choice with respect to the aerodynamics for heating air, particularly when the space for the respective air-flow conducting channels is very limited, as is the case in motor vehicles. Therefore, it was logical for the ventilator module for vehicle seats according to EP 1 479 918 A1 to use a radial ventilator. However, it is known that radial ventilators are not particularly suitable for this purpose, because they create high pressure with respectively high exiting flow speeds.
Furthermore, an automated production of the known electric heating modules is hardly possible due to their multi-layered, spring-loaded structure within a frame. Rather, a high degree of manual labor is necessary.
Another example for a ventilator module for motor vehicle seats is found in EP 1 464 533 A1. U.S. Pat. No. 6,541,757 B1 shows an example for a heating module provided with a blower and resistance heating wires in the air flow, like in hair dryers, and integrated in a vehicle seat.

SUMMARY

Starting with this prior art, the present invention is based on the objective of improving an electric heating module of the type mentioned at the outset with regard to automated manufacturing.
This objective is attained by an electric heating module having the features of claim 1. Preferred embodiments and further embodiments of the invention are described in claims 2 through 14. A preferred use of the heating module according to the invention is found in claim 15.
According to the present invention an electric heating module of the type mentioned at the outset is modified in that the heat conducting ribs are formed from strips, which are connected in the area of the PTC-heating element into at least one packet of strips. This packet of strips is formed from bars being in a heat-conducting contact to one another, while the strips in the heat dissipation area are fanned out such that air can flow through them. The heat transfer from the PTC-heating element into the ribs occurs therefore in an area, in which the ribs are combined to a compact packet and act as a massive block, in which the heat of the PTC-heating element distributes rapidly. Where the ribs extend into the heat dissipation area they are fanned, through, i.e. each being at a distance from one another, by being increasingly angled at the transfer section to the heat dissipation area towards the edge regions of the packet of strips. Good heat conduction occurs within the individual ribs so that the heat in the heat dissipation area can be released very efficiently to the air flowing through. Simultaneously, the production of such strips in the form of ribs and combining them to packets of strips as well as the fanning of the ribs in the heat dissipation area allow it to be produced entirely in an automated fashion and furthermore makes it very efficient and cost effective.
The fanning of the heat conducting ribs formed from strips according to the invention, starting from the area of the PTC-heating element, in which the ribs are combined to packets of strips, naturally causes a fan-shaped arrangement of the ribs in the heat dissipation area so that it has a beneficially curved shape. Particular advantages result from the heat dissipation area being embodied accordingly in a circular shape, in particular round, and surround the area of the PTC-heating element in a plane positioned approximately perpendicular to the air flow. Thus, in this circular heat dissipation area the ribs extend essentially radially so that the electric heating module according to the invention can be inserted into a cylindrical, aerodynamically beneficial air flow channel or a respective pipe. In this manner, a very homogenous flow through the heat dissipation area is ensured without forming heat pockets, such as e.g. in the corners of a conventionally rectangular, cellular arranged heating module. But primarily a heating module with a circular heat dissipation area is suitable for an efficient combination with an axial or diagonal fan; this can be inserted very easily in front or behind the heating module according to the invention in order to form a ventilating heater safe from overheating.
The PTC-heating element can be located between two packets of strips and contact them not only in a heat-conducting fashion but also electrically conducting. When simultaneously an electrically insulating frame element is provided, which is arranged between the two packets of strips and accepts the PTC-heating element, the PTC-heating element can be supplied with power via the packets of strips. This occurs simply in that the first packet of strips is located at one side of the PTC-heating element and connected to the other electrical potential than the other packet of strips at the other side of the PTC-heating element so that the current can flow through the PTC-heating element necessary for heating it. In this way, the PTC-heating element can be integrated in the packet of strips in a very compact fashion, in particular assembled therein in an automated manner, so that respective advantages result with regard to a compact construction, efficient heat transfer, as well as easy automatic manufacturing.
The electric insulating frame element can not only separate the packet of strips from one another, but can also be embodied in the form of a rib and extend into the heat dissipation area. This way it is ensured that in the heat dissipation area no unintended electrically conducting bridge can develop between the ribs of one packet of strips and ribs of the other packet of strips. Additionally, the frame element can then be provided with assembly elements for connecting them to a housing for the module, which again facilitates the automatic machine production.
In this context it must be mentioned that, of course, in a heating module according to the invention three or more packets of strips having PTC-heating elements positioned therebetween and, if necessary, corresponding electrically insulating frame elements can be combined to a single module as well.
In order to electrically contact the PTC-heating element, contacting links can be arranged in or at the packets of strips, which are connected to the power supply. This also increases the potential level of automation during the machine production of the heating module according to the invention.
When an electrically insulating frame element is provided between the packet of strips, in which the PTC-heating element is integrated it is preferred for the PTC-heating element to be surrounded by a soft-elastic sealing layer located in the electrically insulating frame element. This soft-elastic sealing layer may comprise an O-ring, which again facilitates the production enormously, or a soft-elastic component of the material of the frame element. In the latter case, the frame element could be produced, for example, from plastic, using a two-component injection technique. In addition to the mechanical protection for the PTC-heating element during the assembly, such a soft-elastic seal also offers protection from moisture, which can be rather important for a heating module to be mounted in a seat.
The heat-conducting ribs preferably comprise aluminum or copper sheet metal strips. Said materials offer high heat conductivity and can be processed rather easily in an automated fashion.
The packets of strips, to which the heat-conducting ribs are combined in the area or the PTC-heating element, are preferably held together by welding, for example using a laser welding seam or the like. Additionally, the packets of strips can be pressed toward one another by a spring-loaded clamp. This spring-loaded clamp can preferably hold not only the respective packets of strips but all packets of strips with the PTC-heating element located therebetween and compress them such that the heat exchange between the PTC-heating element and the packets of strips as well as between the individual ribs is optimized.
For a simple and accurately positioned machine production, the ribs embodied as strips can additionally be provided with centering bores for a correctly positioned stacking during the assembly.
When a housing is provided, into which the electric heating module according to the invention is integrated, it is preferred for said housing to form a cylindrical or, for the purpose of noise reduction, a conical air flow channel, in which the heating module and downstream and/or upstream in reference to a heating module, an axial or diagonal fan is accepted.
The axial or diagonal fan can be a conventional fan with a fan housing and electric connectors, so that it is useful for the housing of the heating module according to the invention to accept the axial or diagonal ventilator including its own ventilator housing.
A particular advantage of the electric heating module according to the present invention results when it is used as a ventilator in a ventilated seat, in particular a vehicle seat, in which the heating of the airflow can be switched on, if necessary, to serve as a seat heater using the PTC-heating element and the heat conducting ribs.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, an embodiment of the present invention is described and explained in greater detail using the attached drawing. It shows:
FIG. 1 a perspective view of a heating module according to the invention;
FIG. 2 a top view of the heating module of FIG. 1;
FIG. 3 a perspective exploded view of the heating module of FIG. 1;
FIG. 4 a heating module of FIG. 1 with a housing and fan, prior to the assembly;
FIG. 5 the heating module assembled in the housing in a perspective top view;
FIG. 6 a perspective view of the heating module assembled in the housing, seen from below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The completely assembled exemplary embodiment of an electric heating module according to the present invention, shown in a perspective view in FIG. 1, comprises a multitude of heat-conducting ribs 1, made from aluminum sheet metal strips and radially filling a circular heat dissipation area 2. In the center of the heat dissipation area 2 the heat conducting ribs 1 are combined to a total of four packets of strips 3, with the ribs 1 of each packet of strips 3 being closely packed and contacting one another in a heat conducting and electrically conducting manner. Using welding seams 4 the ribs 1 of the individual packets of strips 3 are fixed to one another.
Two electrically insulating frame elements 5 are arranged between the packets of strips 3, which insulate the two central packets of strips 3 each from the exterior packets of strips 3. The frame elements 5 extend from the central area inside the heat dissipation area 2 towards the heat dissipation area 2 and continue towards the assembly elements 6, at which a housing and a fan can be attached, as described below.
The two central packets of strips 3 are only separated from one another by a contact bar 7, by which the PTC-heating elements (here not shown) integrated in the frame elements 5 can be connected to a power supply (not shown). Additional contact bars 7 are provided at the edge region of the exterior packet of strips 3 in order to also connect the respective other contact surfaces of the PTC-heating elements to the power supply.
The electrical contacting is illustrated with charge symbols in FIG. 2, which is a top view of the electrical heating module of FIG. 1. The central contact bar 7, symbolized with a plus sign, is switched to another electric potential than the two exterior contact bars 7, which are marked with a minus sign. Due to the fact that the ribs 1 in the central area around the two PTC-heating elements located in the frame elements 5 are supported on one another over their entire surface they not only form a good heat conductor but also a good electric conductor so that the current from the contact bars 7 reach the PTC-heating elements via the packets of strips 3. The electrically insulating frame elements 5 ensure that no short can develop in the area of the packets of strips 3 or in the heat release area 2.
In FIG. 3, an exploded view of FIG. 1, it is discernible how the two now visible PTC-heating elements 8 are integrated in the frame elements 5. The frame elements 5, additionally provided at the top and the bottom with assembly frames 9 for an exact positioning, are provided with a circular recess 10, into which the PTC-heating elements 8 and an O-ring 11 can be inserted in a form-fitting manner. The heat-conducting ribs 1 are combined to packets of strips 3 in their central areas, while they radially fan out in the heat dissipation area 2. The packets of strips 3 are fixed via welding seams 4. The ribs 1 are provided with central bores 12, by which they can be stacked exactly in order to form the packets of strips 3. After the assembly of the four packets of strips 3 and the two frame elements 5 with the two PTC-heating elements 8 as well as the assembly therebetween and/or superimposition of the contact bars 7 the entire module is finally fixed with the spring-loaded clamp 13. In addition, the spring-loaded clamp 13 permanently presses the packets of strips 3 towards one another so that the packets of strips 3 positioned at both sides of the PTC-heating elements 8 are pressed against the PTC-heating elements in order to ensure an optimal contact.
Using the FIGS. 1 through 3, it is discernible that the heating module according to the invention can be very easily assembled, in particular assembled and produced automatically by machines without any problems. As described in the following, the insertion into a housing and the attachment of a fan are also possible very easily just as the electrical contact of the module via the contacting bar 7.
FIG. 4 shows a perspective view of the electric heating module of FIGS. 1 through 3, a housing 14, and an axial fan 15 prior to their assembly. The axial fan 15 comprises a commercial axial fan with a rotor 16, a motor 17, and a housing ring 18. The housing 14 comprises a cylindrical heat exchange area 19, a cylindrical fan area 20, and an air output opening 21, which is provided with air directing bars 22. A type of assembly flange 23, having centering pins 24, is formed at the housing 14. In order to allow the axial fan 15 to be inserted together with its housing 18, without having to modify it, the ventilator area 20 is expanded in reference to the heat exchange area 19, into which the heating module is to be inserted. For this purpose, the assembly elements 6 of the frame element 5 serve to fix the housing ring 18 of the axial fan 15 in the right position in reference to the ribs 1 and to hold them fixed in the housing 14. An opening 25 in the housing serves to guide cables for the power supply of the motor 17 of the axial fan 15 as well as to connect the PTC-heating elements via the contact bars 7 to the power supply.
In the FIGS. 5 and 6, perspective representations of the assembled arrangement of FIG. 4 are shown from the top and the bottom. Using these drawings, the present invention shows the compact and easily automatically assembled construction of the ventilator with air flow heating, in particular for an assembly into ventilated seats. Simultaneously, using the FIGS. 1 through 6, it is discernible that the heating module according to the invention can be automatically produced and assembled without any problems with a very high degree of automation. The housing 14, shown in FIGS. 5 and 6 and provided with an electric heating module and an axial fan 15, can be used both for ventilation, for example of a vehicle seat, or when the PTC-heating element is activated, for heating of a seat with a very efficient air flow heating, with the air flow heater being provided with heat-conducting ribs 1 arranged radially, with a circular heat dissipation area 2 producing a very even temperature distribution in the housing 14, and ultimately in the seat. Due to the particulars of the PTC-heating elements, here a very high initial power is provided for heating, while due to the positive temperature characteristic the PTC-heating elements ensure a tolerable maximum temperature under all circumstances, i.e. even during malfunctions.

Claims

1. An electrical heating module for heating an air flow for heating and ventilating seats, comprising at least one PTC-heating element (8) and at least one heat dissipation area (2) adjacent thereto which allows air to flow therethrough, with heat-conducting ribs (1), which are in an effective connection to the PTC-heating element (8) and are combined together to form a module, the heat-conducting ribs (1) are formed from strips, which are combined in an area of the PTC-heating element (8) to form at least one packet of strips (3) formed by the ribs (1) in a heat-conducting contact with one another, and which are fanned out in the heat dissipation area (2).

2. An electric heating module according to claim 1, wherein the heat dissipation area (2) is generally circular and encircles an area of the PTC-heating element (8) in a plane aligned approximately perpendicular to the air flow.

3. An electric heating module according to claim 1, wherein the PTC-heating element (8) is located between two packets of the strips (3) and contacts them both in a heat-conducting as well as an electrically conducting manner, and an electrically insulating frame material (5) is arranged between the two packets of strips (3), into which the PTC-heating element (8) is integrated, and the PTC-heating element (8) is supplied with power via the packets of strips (3).

4. An electric heating element according to claim 3, wherein the frame element (5) is provided in the form of a rib (1) that extends into the heat dissipation area (2).

5. An electric heating module according to claim 4, wherein the frame element (5) is provided with assembly elements (6) for mounting to a housing (14) for the module.

6. An electric heating module according to claim 4, wherein contact bars (7) are provided in or at the packets of strips (3) for supplying power to the PTC-heating elements (8).

7. An electric heating module according to claim 3, wherein the PTC-heating element (8) is surrounded by a soft-elastic sealing layer located in the electrically insulating frame element (5).

8. An electric heating element according to claim 7, wherein the soft-elastic sealing layer is an O-ring (11) or a soft-elastic component of a material which forms the frame element.

9. An electric heating module according to claim 3, wherein the packets of strips (3) are held together by a welding seam (4).

10. An electric heating module according to claim 1, wherein the heat conducting ribs (1) comprise aluminum or copper sheet metal strips.

11. An electric heating module according to claim 10, wherein the sheet metal strips are provided with centering bores (12) for a correctly positioned stacking during assembly.

12. An electrical heating module according to claim 1, wherein the packets of strips (3) are compressed against one another by a spring-loaded clamp (13).

13. An electric heating module according to claim 5, wherein the housing (14) forms a cylindrical or conical air flow channel, in which the heating module and, an axial or diagonal fan (15) is located downstream and/or upstream of the heating module.

14. An electric heating module according to claim 13, wherein the axial or diagonal fan (15) is positioned in a fan housing (18) of its own, which is accepted in the housing (14).

15. An electric heating module according to claim 1, wherein the heating module is connected to a ventilated seat to provide an air flow that can be heated to the seat.

16. An electric heating module according to claim 15, wherein the seat is a vehicle seat.