Thermoelectric device

A thermoelectric device may include a plurality of electrically conductive first threads and a plurality of electrically insulating second threads structured and arranged to define a fabric. At least one first thread of the plurality of first threads may include a plurality of p-doped thread sections and a plurality of n-doped thread sections arranged in alternating relationship with one another. The plurality of first threads may extend in a wavy course defining a plurality of curvature-turning points. The plurality of p-doped thread sections and the plurality of n-doped thread sections may be arranged in a respective curvature-turning point of the plurality of curvature-turning points.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to International Patent Application No. PCT/EP2016/071714, filed on Sep. 14, 2016, and German Patent Application No. DE 10 2015 217 754.8, filed on Sep. 16, 2015, the contents of both of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The invention relates to a thermoelectric device, in particular for an air conditioning system of a motor vehicle, and to an air conditioning system having at least one such thermoelectric device.

BACKGROUND

In the vehicle interior, motor vehicles have a multiplicity of surfaces which because of their high surface temperature greatly heat up the vehicle interior when the vehicle is exposed to insolation over an extended period of time. Said surfaces therefore have to be initially at least surface-cooled by an air conditioning system of a motor vehicle in order to establish ambient conditions that are acceptable to the occupants of the motor vehicle. Desirable for this reason is a technology which brings about a rapid cooling of the surfaces of the vehicle interior even in the first seconds following the start-up of the air conditioning system.

In conventional motor vehicles, the cooling of the interior is exclusively accomplished by means of evaporation cooling by transferring cold to air flowing into the interior. Warm surfaces, which radiate into the interior, are thus only gradually cooled through convective transfer of heat to the flowing air.

Devices with shorter cooling time merely exist for surfaces in direct contact with the occupants: accordingly, an active seat cooling is known from the prior art for vehicles of the luxury class, in the case of which air flowing into the seat is actively cooled via Peltier element and flows out towards the occupant via pore-like apertures above the seat surface. Such a Peltier element comprises p and n-doped semiconductors, which are arranged alternately and electrically in series with each other. Electrically conductive contact bridges between the doped regions serve as heat absorption or heat emission element. In order to thermally and spatially separate a hot side from a cold side, these are alternately attached to a top or a bottom side of the Peltier element.

DE 195 03 291 C2 discloses a heating-cooling mat for a vehicle seat. The same comprises an air conditioning mat in which multiple Peltier elements are arranged, which for the voltage supply can be connected to an electrical system of a motor vehicle.

DE 10 2012 018 387 A1 deals with a thermoelectric generator having a thermoelectric substrate and a multiplicity of thermal pairs, wherein each thermal pair comprises a first thermoelectric conductor of a first thermoelectrically active material and a second thermoelectric conductor of a second thermoelectrically active material.

DE 10 2013 110 254 A1 deals with a thermoelectric element which comprises electrically conductive threads, thread bundles or filaments. These are designed in the form of conductive strands passing through a substrate.

EP 1 340 060 B1 deals with a method for producing thermoelectric converters with multiple thermoelectric elements arranged in series. By interweaving electrically conductive wires of two different materials, which are alternately arranged in parallel, these are formed with wires of electrically insulating material.

Disadvantageous in using conventional Peltier elements for actively cooling a vehicle interior is that the same are not suitable for cooling large-area surfaces.

SUMMARY

The present invention is based on the object of creating a thermoelectric device which is suitable for cooling heated-up surfaces with large surface area, in particular in the vehicle interior of a motor vehicle.

According to the invention, this object is solved through the subject matter of the independent patent claim(s). Advantageous further developments are the subject matter of the dependent patent claim(s).

Accordingly, the basic idea of the invention is to form a thermoelectric device as fabric with electrically conductive warp threads and with electrically insulating weft threads, or vice versa. This makes possible forming the thermoelectric device as flexible flat structure, which can be employed as part of a cooling device in an air conditioning system over a large area.

A thermoelectric device according to the invention comprises a plurality of electrically conductive first threads and a plurality of electrically insulating second threads which together form a fabric. The first threads can be warp threads of the fabric, and the second threads can be weft threads of the fabric or vice versa. For the thermoelectrically active design of the fabric, a plurality of p-doped and n-doped thread sections is alternately present in at least one first thread. Preferably, this applies to multiple, i.e. for at least first threads, particularly preferably to all first threads of the fabric. Each of the electrically conductive first threads not only forms a thermoelectric element but—depending on position relative to the electrically insulating second threads—also a hot side or a cold side of the thermoelectric device in sections.

Here, the term “fabric” expressly includes forms of realisation with which the person skilled in the art of textile technology is familiar under the designations “plain weave”, “twill weave” and “satin weave”.

Preferably, the second threads are of a thermally insulating design. In this way, undesirable heat bridges between the hot side and the cold side can be prevented.

In a further preferred embodiment, the first threads arranged in the fabric follow a wavy course with a plurality of curvature turning points, wherein the p and n-doped thread sections are arranged in the region of a respective curvature-turning point of the first thread. Non-doped regions between the thread sections can then function as hot side or cold side.

In a further preferred embodiment, the fabric is designed as flat structure. This makes possible using the fabric over a large area on surfaces that are not flat, such as are often present in the interior of a motor vehicle.

In order to achieve as high as possible an efficiency in the thermoelectric device according to the invention, the p-doped and the n-doped thread sections are arranged, in a further preferred embodiment, in the first threads in such a manner that a first side of the fabric forms a hot side and a second side of the fabric located opposite the first side forms a cold side, or vice versa.

In an advantageous further development of the invention, the first threads each comprise an electrically conductive conductor, preferentially of a metal, particularly preferably of copper, which is surrounded by an electrically insulating sheath. Preferably, the sheath consists of plastic. In this way, undesirable electrical short-circuits of individual electrically conductive first threads among each other or with other electrically conductive materials, which are present in the surroundings of the fabric, can be excluded.

In another preferred embodiment, the first threads and/or the second threads are formed ribbon-like. Such a flat formation of the first or second threads increases the cooling output that can be provided by the same, in particular when used in an air conditioning system.

Particularly practically, the individual first threads extend along a first direction, whereas the second threads extend along a second direction, which runs transversely to the first direction.

In a further preferred embodiment, all present first threads are connected electrically in series with each other. This reduces the wiring expenditure when connecting the first threads to an electric voltage source. This in turn results in substantial cost savings in producing the thermoelectric device.

In an advantageous further development, all present first threads can be integrally moulded one against the other. The resulting total thread can be particularly cost-effectively produced and particularly easily processed with the second threads to form a fabric. Furthermore, all first threads with this version do not have to be individually designed for connection to an electric voltage source but it is rather sufficient to connect the total thread with both its ends to such an electric voltage source. This likewise produces reduced manufacturing costs.

In an advantageous further development it is conceivable to combine an electric series connection and an electric parallel connection of the first threads with each other.

Particularly practically, the present first threads can be arranged, in a top view of the first and/or second side of the fabric, in a meander-like manner. In this way it can be ensured that on the cold side a homogeneous cooling output is achieved areally.

In another preferred embodiment, at least two, preferentially all, first threads can be electrically interconnected parallel to each other. In this way, the magnitude of the electric supply voltage required for operating the first threads as thermoelectric device—in particular compared with an electric series connection, can be reduced.

Since the fabric of the thermoelectric device itself only has a relatively low thermal capacity, it can generate a thermal cooling effect on the cold side only for a short time when loosely placed. Particularly practically, an additional heat accumulator for the buffer storing of heat can therefore be arranged on the hot side, which for the thermal coupling lies against the first threads. Said heat accumulator serves to absorb and temporarily buffer-store heat made available on the hot side.

Particularly preferably, the heat accumulator can be formed as heat accumulator plate, which is attached to the first threads by means of a thermally conductive adhesive material. This allows areally connecting the heat accumulator to the hot side of the thermoelectric device. Preferentially, the thermally conductive adhesive means is an adhesive.

Particularly practically, the heat accumulator can comprise a mechanically flexible material. In this way, the desired mechanical and thermal connection to the fabric of the thermoelectric device can be ensured even when the fabric is not designed entirely flat.

A further preferred version proves to be technically particularly easily and thus cost-effectively realisable, in which the heat accumulator comprises a flexible envelope, preferentially of a metal, particularly preferably a metal film. In this version, a liquid or a PCM material for absorbing the heat to be stored is arranged in the flexible envelope.

In a further preferred embodiment, an sheath thickness of the electrically insulating sheath of at least one first thread can be increased in at least one transition region between a p or n-doped thread section and the thread section without doping adjacent thereto for the purpose of pull relief. In this way, the strength of the first thread concerned is significantly improved in particular when subjected to tensile loading.

In another preferred embodiment, a in particular additional sheathing for pull relief can be provided in at least one first thread in at least one transition region between a p or n-doped thread section and the thread section without doping adjacent thereto. “Additional” means that this sheathing can be provided in addition to the electrically insulating sheathing described above. In this way, the strength of the first thread concerned, in particular when subjected to tensile load, is improved. Such “additional sheathing” can also be provided when the electrically insulating sheathing is omitted.

In a version of the invention, the first threads and second threads of the fabric can be switched, i.e. in such a scenario, the first threads have the properties of the previously described second threads and the second threads the properties of the first threads described above.

Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the associated figure description by way of the drawings.

Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference characters relate to same or similar or functionally same components.

DETAILED DESCRIPTION

FIG. 1illustrates the fundamental construction of a conventional thermoelectric element100. The same comprises a plurality of p and n-doped electric semiconductors101a,101b, which are alternately electrically contacted in series with each other. The electrical contacting is affected by means of electrical bridges102a, which simultaneously form a hot side103of the thermoelectric element100, and by means of second electrical bridges102b, which form a cold side104of the thermoelectric element100and are located opposite the first electrical bridges102a.

TheFIGS. 2 and 3illustrate the fundamental construction of a conventional fabric105in a top view of lateral view. According toFIG. 2, the fabric105comprises a plurality of warp threads106which extend along a first direction R1parallel to each other. A plurality of weft threads107extend parallel to each other along a second direction R2, which runs perpendicularly or at least substantially perpendicularly to the first direction R1. The warp threads106are connected to the weft threads107through the connection type “cross hair connection”. This means that the warp threads106alternately extend over and under the transverse weft threads107in a certain rhythm known as “weave” to the person skilled in the art. Accordingly, the warp threads107alternately extend over and below the transverse warp threads106.

FIG. 4now shows an example of a thermoelectric device1according to the invention in a cross section. The thermoelectric device1comprises a plurality of first threads24in the form of electrically conductive warp threads2and a plurality of second threads25in the form of electrically insulating weft threads3which together form a fabric4. The arrangement of the warp threads and weft threads2,3corresponds to the arrangement of the warp threads and weft threads106,107explained for a conventional fabric105by way of theFIGS. 2 and 3. Accordingly,FIG. 4shows the fabric4of the thermoelectric device1according to the invention in a representation which corresponds to that of theFIG. 3for the conventional fabric105. For this reason, only a single warp thread2is shown inFIG. 4which extends along a first direction R1. Furthermore, four weft threads3are exemplarily shown, which extend along a second direction R2, which runs perpendicularly to the first direction R1—in the example ofFIG. 4perpendicularly to the drawing plane.

For forming the fabric4as thermoelectrically active element, a plurality of p-doped thread sections5and n-doped thread sections6are alternately arranged in each warp thread2. The fabric4is preferentially designed as a flat structure23.

According toFIG. 4, the warp threads2in the fabric4follow a wavy course with a plurality of curvature-turning points7. Preferentially, the p and n-doped thread sections5,6are arranged in a respective curvature-turning point7. Adjacent thread sections5,6are preferentially arranged spaced from each other, so that between two adjacent thread sections5,6with p or n-doping a thread section8without doping can be provided in each case. These thread sections8correspond to the first and second electrical bridges102a,102balready shown in connection withFIG. 1.

The p-doped and the n-doped thread sections5,6are arranged in the warp threads2in such a manner that a first side9of the fabric4forms a hot side11and a second side10of the fabric4located opposite the first side9forms a cold side12(seeFIG. 4) or vice versa (not shown in the figures). The thread sections8act as hot side or cold side of the thermoelectric device1depending on the side on which they are arranged relative to the weft threads3.

A warp thread2comprises an electrically conductive conductor13which is surrounded by an electrically insulating sheath. In this way, undesirable electrical short circuits of the electrically conductive warp threads2with other electrically conducting materials in the surroundings of the fabric4of among each other can be excluded. The electrical conductor13is preferably a metal such as for example copper. The sheath preferentially consists of a plastic or comprises such a plastic. A sheath thickness of the electrically insulating sheath14can be increased for the purpose of pull relief in the transition region26between a p or n-doped thread section5,6and the thread section8without doping adjacent thereto.

The warp threads3are preferentially not only designed electrically insulating but also thermally insulating. In this way, undesirable heat bridges between the hot side11and the cold side12can be prevented. In a version that is not shown in the figures, the warp threads2and/or the weft threads3can also be formed ribbon-like for increasing the heat transfer output. The electrically insulating weft threads3can consist of a plastic.

FIG. 5shows a further development of the thermoelectric device1of theFIG. 1. In the version according toFIG. 5, a heat accumulator for buffer-storing heat is arranged on the hot side, which for the thermal coupling lies against the warp threads2. The heat accumulator15can be designed as plate-like heat storage plate16, which is fastened to the warp threads2by means of a thermally conductive adhesive means17, for example a heat-transferring adhesive.

Preferably, heat accumulator15or the heat storage plate16comprises a mechanically flexible material. InFIG. 8, a possible technical form or realising such a mechanically flexible heat accumulator15is schematically shown. The same comprises a flexible envelope18, preferentially of a metal, in which a liquid19or a PCM material20for the buffer storing of the heat is arranged. Particularly preferably, the envelope18can be formed as a metal film.

InFIG. 6, a possible arrangement of the warp threads2and the weft threads3is shown in a top view of the hot side11(an optionally present heat accumulator15is not shown inFIG. 6). As is evident fromFIG. 6, all present warp threads2are moulded integrally against each other and in this way electrically connected to each other in series. The resulting total thread21comprises a first end section22aand a second end section22blocated opposite the first end section22a, which can both be connected to an electric voltage supply (not shown inFIG. 6). The warp threads2forming the total thread21are arranged meander-like in the top view of the first side9or of the hot side11of the fabric4shown inFIG. 6. The individual warp threads2in this version are electrically connected to each other in series so that for operating the thermoelectric device1only the two end sections22a,22bhave to be connected to an electric voltage supply.

Compared with this,FIG. 7shows a version of the arrangement ofFIG. 6in which all existing warp threads2are electrically interconnected in parallel with each other.

FIG. 9shows a further development of the thermoelectric device1of theFIG. 5. Accordingly, an additional sheathing27for the pull relief of the first thread24can be provided in the transition region26of the first thread24between a p or n-doped thread section5,6—FIG. 9exemplarily shows a p-doping—and the thread section8adjacent thereto. The sheathing27can be provided additionally to the electrically insulating sheath14and as shown inFIG. 9extend over the entire p-doped thread section6. The additional sheathing27thus protrudes into the thread section8without doping so that the boundary surfaces28between p or the n-doped thread section5,6and the thread section8without doping are relieved.