EP2276321B1 - Heat exchanger - Google Patents

Description

The invention relates to a heat exchanger according to the preamble of claim 1 and an automotive air conditioning system.

Automotive air conditioning systems serve to heat and / or to cool the air to be supplied to the interior of a motor vehicle. In automotive air conditioning systems, electric heaters are used to heat the air supplied to the interior. The electric heater comprises a heat exchanger with a PTC element. Positive Temperature Coefficient (PTC) elements are current-carrying materials that have electrical resistance and can conduct electricity better at lower temperatures than at higher temperatures. Their electrical resistance thus increases with increasing temperature. The PTC element is generally made of ceramic and is a PTC thermistor. This raises regardless of the boundary conditions - such. B. applied voltage, nominal resistance or air flow to the PTC element - a very uniform surface temperature PTC element. Overheating can be prevented as it z. B. could occur with a normal heat-emitting heating wire, since regardless of the boundary conditions always about the same resistance and thus a substantially identical electrical heating power is applied.

A heat exchanger comprises a PTC element, at least two electrical conductors by means of which electrical current is conducted through the PTC element and heat conducting elements, in particular corrugated fins or fins, by means of which the surface for heating the air increases and thus the heat from the PTC element the heat conducting element and the air is transferred.

The US 4,327,282 shows a heat exchanger with a PTC heating element. Current is passed through the PTC heating element by means of contact plates and an insulating layer is arranged on the contact plates. The components are held together by means of a U-shaped clip.

From the EP 1 768 458 A1 a heat generating element of a heater for air heating is known, comprising at least one PTC element and voltage applied to opposite side surfaces of the PTC element electrical conductor tracks, wherein the two electrical conductors are surrounded on the outside by a non-electrically conductive insulating layer.

The DE 101 18 599 B4 shows an electric heater, in particular as additional heater of a vehicle, with at least one frame part for receiving at least a flat, openings for flow of heating air having grid-like PTC heating element with an elastic means for electrically contacting the PTC heating elements.

The device for electrical contacting of the PTC heating elements is designed as a U-shaped contact spring, the free leg of the PTC heating element spring is resilient and at the same time provides for a tolerances compensating mechanical support of the PTC heating element relative to the frame part.

From the DE 103 33 451 A1 is a device for receiving ceramic heating elements in a heating device with an insulating frame and at least one held by this contact plate on which the heating elements can be placed known. The contact plate and the frame are connected non-positively.

For electrically contacting the PTC heating elements with a current source, contact plates which are in electrical contact with the PTC elements are used directly. The PTC elements are disc-shaped and for passing electrical current through the PTC elements, the contact plate is connected to the PTC element by adhesive bonding on two opposite sides of the PTC elements. On these two contact plates then a corrugated fin part or a lamella part is applied as a heat conducting element for transmitting heat from the PTC elements to a fluid to be heated by means of gluing. At the two outer ends of the corrugated rib parts or the plate parts is ever an additional other contact plate mounted. Thus, six adhesive bonds are required to make the heat exchanger, between the PTC elements and the contact sheets, between the contact sheets and the corrugated fin portions and between the corrugated fin portions and the additional contact sheets at the outer end of the corrugated fin portions. Thus, a high number of components and adhesive joints are required in the manufacture of the heat exchanger.

The object of the present invention is therefore to provide a heat exchanger and a motor vehicle air conditioning system in which the PTC elements can be electrically connected to as few components as possible and a small number of adhesive connections to a power source in order to reduce the manufacturing cost of the heat exchanger , The heat exchanger and the automotive air conditioning system should work reliably in operation.

This object is achieved with a heat exchanger comprising at least one PTC element, at least two electrically conductively connected to the at least one PTC element conductor to conduct electrical current through the at least one PTC element and thereby the at least one PTC element heat, at least one heat conducting element for transmitting heat from the at least one PTC element to a fluid to be heated, and preferably at least one means for connecting the at least one PTC element, the at least two conductors and the at least one heat conducting element to each other, wherein at least one of at least two conductors is also a heat conducting element, wherein at least one PTC element is fixed to a disc-shaped and / or strip-shaped and / or frame-like fastening part, wherein the at least one PTC element is fixed by means of a latching and / or clip connection to the fastening part ,

One of the at least two conductors thus also functions as a heat-conducting element, i. H. one of the at least two conductors serves to transfer heat from the at least one PTC element to a fluid to be heated. In this case, the at least one conductor is a component which is both a conductor and a heating element.

In a further embodiment, the surface of the at least one conductor, which is also heat-conducting element, is larger than the surface at least a PTC element, in particular larger than the surface of all PTC elements of the heat exchanger.

Preferably, the surface of the at least one conductor, which is also a heat-conducting element, is greater than 0.5, 1, 5, 10, 20, 30, 40, 50 or 70 cm ² .

In a further embodiment, the surface of the at least one conductor, which is also a heat-conducting element, is 1.5, 2, 4, 7, 10, 15, 20 and 30 times larger than the surface of the at least one PTC element, in particular as the surface of all PTC elements of the heat exchanger.

A component thus serves both as a conductor and as a heat element, so that at least one component and at least one adhesive connection for connecting the components of the heat exchanger can be saved in the production of the heat exchanger.

In particular, all conductors which are in direct electrical contact with the at least one PTC element are also heat-conducting elements. In the case of direct electrical contact between the conductor and the at least one PTC element, there is no additional conductor between the conductor and the at least one PTC element for conducting the electrical current to the at least one PTC element. In the case of direct electrical contact between the conductor and the PTC element, the conductor can be connected, for example by means of a material connection, for. Example, an adhesive connection, be connected to the at least one PTC element, so that the electrical current is possibly also at least partially passed through the material of the cohesive connection.

In a further embodiment, the heat exchanger comprises two conductors, in particular only two conductors, which are in direct electrical contact with the at least one PTC element, which are also heat-conducting elements, this conductor may for example also be multi-part.

In a supplementary embodiment, the at least one conductor, which is also a heat-conducting element, is an identical component and / or the at least one conductor, which is also a heat-conducting element, is in direct electrical contact with the at least one PTC element.

Preferably, the at least one PTC element is a planar component, wherein the planar component has two opposite surface sides, which have the respective largest surface side of the PTC element. In this case, the PTC component plane is preferably parallel to these two surface sides.

The at least one PTC element is preferably a plate-shaped component which has a greater extent in a PTC component plane than perpendicular to the PTC component plane.

In one variant, the extension perpendicular to the PTC component level of the at least one conductor, which is also a heat-conducting element, is greater than the extent of the at least one PTC element perpendicular to the PTC component plane. The conductor also serves as a heat conducting element and thus has to have a large surface area for the transmission of heat to the fluid to be heated. To achieve this large surface, it is necessary that the conductor and thus the heat element has a correspondingly large extent perpendicular to the PTC component level.

Suitably, the extension is perpendicular to the PTC component level of the at least one conductor, which is also a heat conducting element, at least which is 1.5, 2, 3, 5, 7, 10, 15 or 20 times greater than the extent of the at least one PTC element perpendicular to the PTC component plane.

In a further embodiment, at least one conductor, in particular a corrugated fin part or a fin part, which are also heat-conducting elements, are each arranged on two opposite surface sides of the at least one PTC element which are parallel to the PTC component plane.

In particular, the at least one conductor, which is also a heat-conducting element, a corrugated fin part or a fin part and / or all conductors, which are also heat-conducting elements, are corrugated rib parts or fin parts.

In a supplementary variant, the fastening part is provided with at least one recess and in the at least one recess is ever at least one PTC element, in particular only one PTC element arranged.

According to the invention, the at least one PTC element is fixed to the fastening part by means of a non-positive and / or positive connection, in particular a detent and / or clip connection. The at least one PTC element can thus be easily fixed to the fastening part without a cohesive connection, in particular an adhesive connection.

In a further embodiment, the extent or thickness of the fastening part perpendicular to the PTC component level is smaller than the extent or thickness of the at least one PTC element, so that on at least two opposite surface sides of the at least one PTC element, the at least one PTC element of each At least one conductor, in particular a corrugated fin part or a lamella part, is electrically contacted. The disk-shaped and / or strip-shaped fastening part is aligned parallel to the PTC component plane of the at least one PTC element. The thickness or the extent of the fastening part perpendicular to the PTC component plane is smaller than the extension or thickness of the at least one PTC element perpendicular to the PTC component plane. The at least one PTC element is aligned within the recess to the effect that the at least one PTC element protrudes slightly on both sides of the fastening part. As a result, a planar conductor, in particular the corrugated fin part, can contact the at least one PTC element although the at least one PTC element is arranged in the at least one recess of the fastening part.

In particular, the heat exchanger comprises two contact sheets as conductors and / or the at least one conductor and / or the at least one heat-conducting element and / or the fastening part and / or at least one PTC element are positively and materially connected to each other, in particular by means of an adhesive bond and / or a frame. In a connection by means of the frame, the frame encloses at least partially outer or outermost components of the heat exchanger, so that so that the components or components of the heat exchanger are held together.

In an automotive air conditioning system according to the invention, comprising an electric heating device, the electric heating device is designed according to a heat exchanger described in this application.

In a further embodiment, the motor vehicle air conditioning system comprises a refrigerant evaporator and / or a blower and / or a filter.

In a further refinement, in the motor vehicle air-conditioning system the heating of the air takes place exclusively by means of at least one electric heating device, in particular a heat exchanger described in this application with at least one PTC element.

In a further embodiment, the at least one heat-conducting element has a thermal conductivity of at least 1 W / mK, in particular at least 30 W / mK.

In a further embodiment, the fastening part has an electrical insulation of at least 1 kV / mm, in particular at least 25 kV / mm.

In a variant, the fastening part has a dielectric strength of at least 1 kV perpendicular to a PTC component plane.

Fig. 1

einen Querschnitt einer Kraftfahrzeugklimaanlage,

Fig. 2

eine erste perspektivische Ansicht eines Befestigungsteils eines Wärmeübertragers,

Fig. 3

eine zweite perspektivische Ansicht des Befestigungsteils gemäß Fig. 2,

Fig. 4

eine Teilansicht des Wärmeübertragers und

Fig. 5

eine Teilansicht des Wärmeübertragers mit dem Befestigungsteil und nur einem Wärmeübertrager und nur einem Kontaktblech.

In the following, an embodiment of the invention will be described in more detail with reference to the accompanying drawings. It shows:

Fig. 1

a cross section of an automotive air conditioning system,

Fig. 2

a first perspective view of a fastening part of a heat exchanger,

Fig. 3

a second perspective view of the fastening part according to Fig. 2 .

Fig. 4

a partial view of the heat exchanger and

Fig. 5

a partial view of the heat exchanger with the fastening part and only one heat exchanger and only one contact plate.

Fig. 1 shows an automotive air conditioning system 7. In an air conditioning housing 9 with a bottom wall 10 and an outlet opening 12 is a fan 8, a filter 13, a refrigerant evaporator 14 and an electric heater 15 arranged. The air conditioning housing 9 thus forms a channel 18 for passing the air. Walls 11 of the air conditioning housing 9 have on the inside a surface 19, which delimit the channel 18. The air for the interior of a motor vehicle is passed by means of the blower 8 through the filter 13, the refrigerant evaporator 14 and the electric heater 15. Optionally, the motor vehicle air conditioning system 7 may also comprise a heat exchanger (not shown) through which the coolant of an internal combustion engine flows to heat the air.

In the Fig. 2 to 5 is designed as a heat exchanger 6 electric heater 15 of the motor vehicle air conditioner 7 is shown. The heat exchanger 6 comprises two conductors 3 designed as contact plates 4 in order to be able to pass electrical current through PTC elements 1 as an electrical resistance heating element so that the PTC element 1 heats up due to the electrical resistance. Two heat-conducting elements 2 designed as corrugated rib portions 5 serve both to transfer heat from the PTC elements 1 to the fluid to be heated, namely air, and to conduct electrical current through the PTC elements 1. An identical component thus serves both as a conductor 3 and as a heat conducting element 2, namely the corrugated fin part 5. The two contact plates 4 and the two corrugated ribs 5 consist at least partially of metal, in particular aluminum. The corrugated rib parts 5 and the two contact plates 4 thus have a high thermal conductivity as well as a good current conductivity.

A fastening part 17, which is formed like a frame and strip-shaped with a planar geometry, is provided with recesses 20. The at least partially made of plastic fastening part 17 has in the region of the recesses 20 a plurality of clip connections 21. By means of the clip connections 21, the PTC elements 1 without a cohesive connection, in particular an adhesive bond, on the fastening part 17 are positively and / or positively secured. In this case, the clip connections 21 are partially also elastically deformable, so that it comes to a non-positive connection between the fastening part 17 and the PTC elements 1 due to a bias of the clip connections 21. In Fig. 2 the outer edge of the PTC element 1 is shown by dashed lines. This is in Fig. 2 recognizable that the clip connections 1 are partially deformed during insertion into the recess 20 and thus it comes to the listed non-positive connection between the PTC element 1 and the clip connection 21. The PTC element 1 has a PTC component level 16. It is located in the illustration in Fig. 2 the dashed outer edge of the PTC element 1 shown in FIG Fig. 2 within the PTC component level 16. In Fig. 3 Furthermore, a straight line 25 is shown which is perpendicular to the PTC component plane 16. Furthermore, a PTC element 1 has two surface sides 22. The two surface sides 22 are parallel to the PTC component plane 16 and the two surface sides 22 each represent those sides of the PTC element 1 which have the largest surface respectively. The thickness or the extent of the fastening part 17 in the direction of the straight line 25 is smaller than the thickness or expansion of the PTC elements 1 in the direction of the straight line 25 in an arrangement in the recess 20. In this case, the thickness of the PTC elements 1 corresponds to the distance the two surface sides 22. The clip connections 21 are designed such that the PTC elements 1 are fastened centrally within the fastening part 17, so that the PTC elements 1 slightly in the direction of the straight line 25 from the recesses 20 with respect to the remaining part of the fastening part 17 stand out.

The two contact plates 4, the two corrugated rib parts 5 and the fastening part 17 are layered or sandwiched one above the other ( 4 and 5 ). In Fig. 4 the entire heat exchanger 6 is partially shown and in Fig. 5 are the upper contact plate 4 and the upper corrugated rib portion 5 according to Fig. 4 not shown. The two contact plates 4, the two corrugated rib parts 5 and the fastening part 17 with the PTC elements 1 in the recesses 20 are connected to each other by means of an adhesive connection, not shown. The two contact plates 4 have at the ends plug 23 with electrical contact elements 24. At the contact elements 24, an unrepresented electrical mating connector can be inserted with an electrical contact element, not shown, so that the two contact plates 4 can be connected to a voltage source. The introduced into a contact plate 4 current thus flows, for example, from in Fig. 4 shown upper contact plate 4, through the corrugated fin part 5 and then through the PTC elements 1, then through the lower corrugated fin part 5 and then out of the lower contact plate 4 through the lower contact plate 4 with the electrical contact element 24 out. The corrugated ribs 5 can easily contact the PTC elements 1, because the PTC elements 1 slightly protruding from the recesses 20 with respect to the fastening part 17.

The extent of the corrugated rib portion 5 in the direction of the straight line 25 is substantially greater than the extent or the thickness of the PTC element 1. Further, the corrugated fin portion 5 has a much larger surface than a PTC element 1, in particular all PTC elements 1, on and also a much larger surface than the contact plate 4. The corrugated ribs 5 serve both for passing electricity and for transferring heat from the at least one PTC element 1 to the air as the fluid to be heated. The large surface and the large extent in the direction of the straight line 25 of the corrugated fin part 5 is required so that sufficient heat can be transferred from the PTC elements 1 through the corrugated fin part 5 to the air as the fluid to be heated. Within the heat exchanger 5 a total of only four adhesive joints are also required. Namely two adhesive joints between the contact plates 4 and the corrugated rib parts 5 and between the corrugated rib parts 5 and the PTC elements 1 and the fastening part 17th

Overall, significant advantages are associated with the heat exchanger 6 according to the invention and the motor vehicle air conditioning system according to the invention. A component, namely the corrugated fin part 5, serves both as a heat transfer element 2 for transferring heat from the PTC elements 1 to the air and as electrical conductors 3 to conduct electrical current through the PTC elements 1 and thereby the PTC elements 1 to heat. This can be saved in an advantageous manner in the heat exchanger 6 components as well as adhesive joints. The manufacturing cost of the heat exchanger 6 can be lowered and the reliability can thus be advantageously increased.

LIST OF REFERENCE NUMBERS

1

PTC element

2

thermally conductive element

3

ladder

4

contact sheet

5

Well rib part

6

Heat exchanger

7

Automotive air conditioning system

8th

fan

9

Air conditioning case

10

bottom wall

11

wall

12

outlet opening

13

filter

14

Refrigerant evaporator

15

Electric heater

16

PTC component level

17

attachment portion

18

channel

19

surface

20

recess

21

clip connection

22

Surface side of the PTC element

23

plug

24

Electrical contact element

25

Just

Claims (13)

1. A heat exchanger (6), comprising

   - at least one PTC element (1),

   - at least two conductors (3) which are connected to the at least one PTC element (1) in an electrically conducting manner in order to conduct electric current through the at least one PTC element (1) and thus heat the at least one PTC element (1),

   - at least one heat conducting element (2) for transferring heat from the at least one PTC element (1) to a fluid to be heated and

   at least one means for connecting the at least one PTC element (1), the at least two conductors (3) and the at least one heat conducting element (2) to one another, wherein at least one of the two conductors (3) also is a heat conducting element (2), characterised in that at least one PTC element (1) is fixed on a disc-shaped and/or strip-shaped and/or frame-like fixing part (17), wherein the at least one PTC element (1) is fixed on the fixing part (17) by means of a snap and/or clip connection.
2. The heat exchanger as claimed in claim 1, characterised in that all conductors (3) which are in direct electrical contact with the at least one PTC element (1) also are heat conducting elements (2).
3. The heat exchanger as claimed in claim 2, characterised in that the heat exchanger (6) comprises two conductors (3), in particular only two conductors (3), which are in direct electrical contact with the at least one PTC element (1), which also are heat conducting elements (2).
4. The heat exchanger as claimed in one or more of the preceding claims, characterised in that the at least one conductor (3) which also is a heat conducting element (2) is an identical component and/or the at least one conductor (3) which also is a heat conducting element (2) is in direct electrical contact with the at least one PTC element (1).
5. The heat exchanger as claimed in one or more of the preceding claims, characterised in that the at least one PTC element (1) is a plate-shaped component which has a larger extension in a PTC component plane (16) than perpendicular to the PTC component plane (16).
6. The heat exchanger as claimed in claim 5, characterised in that the extension of the at least one conductor (3) which also is a heat conducting element (2) perpendicular to the PTC component plane (16) is larger than the extension of the at least one PTC element (1) perpendicular to the PTC component plane (16).
7. The heat exchanger as claimed in claim 6, characterised in that the extension of the at least one conductor (3) which also is a heat conducting element (2) perpendicular to the PTC component plane (16) is at least 1.5, 2, 3, 5, 7, 10, 15 or 20 times larger than the extension of the at least one PTC element (1) perpendicular to the PTC component plane (16).
8. The heat exchanger as claimed in one or more of the preceding claims, characterised in that at least one respective conductor (3), in particular a corrugated part (5) or a lamella part, which also are heat conducting elements (2), is arranged on two opposite surface sides (22) of the at least one PTC element (1) which are parallel to the PTC component plane (16).
9. The heat exchanger as claimed in one or more of the preceding claims, characterised in that the at least one conductor (3) which also is a heat conducting element (2) is a corrugated part (5) or a lamella part and/or all conductors (3) which also are heat conducting elements (2) are corrugated parts (5) or lamella parts.
10. The heat exchanger as claimed in one of claims 1 to 9, characterised in that the fixing part (17) is provided with at least one recess (20) and at least one respective PTC element (1) is arranged in the at least one recess (20).
11. The heat exchanger as claimed in one or more of the preceding claims, characterised in that the extension or thickness of the fixing part (17) perpendicular to the PTC component plane (16) is smaller than the extension or thickness of the at least one PTC element (1), so that the at least one PTC element (1) can be electrically contacted by at least one respective conductor (3), in particular a corrugated part (5) or a lamella part, on two opposite surface sides (22) of the at least one PTC element (1).
12. The heat exchanger as claimed in one or more of the preceding claims, characterised in that the heat exchanger (6) comprises two contact sheets (4) as conductors (3) and/or the at least one conductor (3) and/or the at least one heat conducting element (2) and/or the fixing part (17) and/or at least one PTC element (1) are connected to one another in a positive and firmly bonded manner, in particular by means of an adhesive bond and/or a frame.
13. A vehicle air-conditioning system (7), comprising an electrical heater (15), characterised in that the electrical heater (15) comprises at least one heat exchanger (6) according to one or more of the preceding claims.

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