PTC heating device and electric heating device comprising PTC heating device

Abstract

The utility model relates to a PTC (Positive Temperature Coefficient) heating device (10), which is provided with at least one PTC element (16); and conductors (20) assigned to different electrical polarities and electrically connected to the PTC element (16); and an electrical insulator covering the PTC element (16) and the conductor (20), in which the electrical insulator is a tube (24) of a collapsible plastic material adapted to reduce at least the diameter of the tube (24) via contraction, and the tube (24) contracts around the PTC element (16) and the conductor (20). In a method for producing such a PTC heating device (10), conductors (20) assigned to different electrical polarities are electrically connected to at least one PTC element (16) and are introduced into a tube (24) made of an electrically insulating collapsible plastic material. The tube (24) is contracted to provide a tight circumferential sleeve around the at least one PTC element (16) and the conductor (20).

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of PTC heating device and the electric heating device comprising such PTC heating device. Furthermore, the utility model relates to a kind of method of manufacturing corresponding PTC heating device. From EP1768457B1, a general PTC heating device is known, the PTC heating device has positioning frame defining the seat for at least one PTC element, as the PTC element in the utility model is ceramic stone, the ceramic stone is generally provided with metallization on opposite surface of ceramic stone, for making stone contact with conductor, the conductor is used to supply electric energy. PTC element has self-regulating property, according to the self-regulating property, the resistance of PTC element sharply increases with specific temperature (so-called Curie temperature). BACKGROUND

[0002] The PTC heating device according to the preamble of claim 1 is used as a heat generation device in a PTC heating device used in a vehicle in particular. While the first electric heating device is operated at 12 volts in a vehicle, electrically powered vehicles require electric heating devices for heating passenger compartments and / or certain components of electric drive concepts (like e.g. batteries) on the one hand. On the other hand, the electric heating devices are operated at a higher voltage for operating electric motors that move the vehicle forward. This results in the need to properly electrically insulate the PTC elements and the conductors from the environment.

[0003] The above prior art discloses a positioning frame that receives a row of a plurality of PTC elements and circumferentially surrounds the respective PTC elements. The opposite main side surfaces are covered with a hybrid electrical insulation that comprises a ceramic sheet and a plastic film connected to the ceramic plate.

[0004] Due to the self-regulating property of the PTC elements, a sufficient thermal contact between the heat dissipation surface of the PTC elements and the medium to be heated is required. Typically, the heat dissipation surface is the main side surface of the PTC element against which a conductor sheet can be contacted that is in turn covered on the other side by an electrical insulation. For a good electrical and thermal contact, those layers have to be in sufficient contact with each other. This can be done by gluing the layers together under pretension. An outer metal housing can be provided that receives the PTC elements, the conductors and the electrical insulation, the metal housing is deformed to abut the layers within the housing under pretension. SUMMARY

[0005] It is an object of the utility model to provide a PTC heating element that can be manufactured economically and thus easily.

[0006] As a solution to the above problems, the utility model provides form the electric insulator through the pipe of the contractible plastic material. The contractible plastic material is usually a heat contractible plastic material, and is adapted to reduce at least the diameter of the plastic pipe via contraction, in particular heat contraction. In the PTC heating device according to the utility model, the plastic pipe is contracted around the PTC element and the conductor. Thus, the element required for energizing the PTC element is received in an electrically insulating sleeve provided by the pipe. Furthermore, the pipe is contracted around the PTC element, and the conductor will form a tight sleeve, and thus will contact the different components within the pipe, typically by biasing those components against each other. This not only provides a good electrical contact between the conductor and the PTC element, but also provides a sufficient thermal contact between the PTC element, the conductor and / or the plastic material providing the plastic pipe. Thus, a good thermal conductivity is provided between the heat generating PTC element and the outer circumferential surface of the pipe.

[0007] According to a preferred embodiment of the utility model, at least one electrically insulating cover is arranged opposite at least one main side surface of the PTC element and within the contracted pipe. The main side surface of the PTC element is a side surface of a regular cubic PTC element, which side surface has at least four times the surface area of any other surface of the PTC element. According to this proposal, a further electric insulator is provided, which is provided in the form of a cover received within the pipe. The respective cover can be provided in the form of a ceramic plate, or can be a hybrid insulating cover comprising a ceramic plate and a plastic foil. The electrically insulating cover is preferably arranged on the outer side of the conductor. Preferably, each conductor is covered by a separate electrically insulating cover on the outer side. The conductor and the electrically insulating cover are each arranged parallel and opposite to an opposite main side surface of the PTC element.

[0008] As generally known, the conductor can be formed by a sheet metal conductor. Those sheet metal conductors according to preferred embodiments of the utility model are kept in good electrical and thermal contact with the PTC element by the radial pretension exerted by the contracted pipe.

[0009] The electric heating device according to the second aspect of the utility model has a housing defining a heating chamber. Furthermore, the housing can define a connection chamber or a control chamber, wherein a plurality of PTC heating devices are electrically contacted and / or a control device for regulating the heat output of the electric heating device is arranged in the control chamber. The heating chamber defined by the housing is provided to dissipate the heat generated by the PTC heating device to a medium to be heated. Thus, the PTC heating device is mainly arranged within the heating chamber. The outer circumferential surface of the contracted pipe is exposed within the heating chamber, and thus will provide a heat dissipation surface on which the medium is heated.

[0010] In the case of the third aspect, the utility model proposes a method for manufacturing a PTC heating device. In the method, the conductors assigned to different polarity are electrically connected to at least one PTC element and are introduced into a tube made of electrically insulating shrinkable plastic material. The tube is then shrunk to provide a tight circumferential sleeve around the at least one PTC element and the conductors. In case a plurality of PTC elements is provided, those PTC elements are usually received in receptacles of a positioning frame having receptacles for at least one PTC element. The positioning frame is usually clamped between the conductors in particular in case the conductors are provided by sheet metal conductors. The additional electrically insulating cover already discussed above is usually arranged opposite one main side surface of the PTC elements. The PTC elements and the conductors and the electrically insulating body are introduced into the tube before shrinking. Shrinking results in a tight contact of all layers and elements contained within the shrinkable tube.

[0011] The shrinkable tube is usually open to both axial ends. One end can be protruded by the positioning frame. Shrinking of the tube on this end can also seal the tube against the outer circumferential surface of the positioning frame. Before shrinking, the positioning frame can be provided with an elastic seal or a curable plastic material, into which the shrinkable tube shrinks upon curing of the curable material and thus provides a tight seal at one end of the positioning frame. A corresponding technique can be used on the other side, on which the positioning frame usually protrudes by terminal lugs for electrical contact between a power source within the electric heating device and the conductors. Usually, those terminal lugs are formed in one piece with the sheet metal conductors, if provided. BRIEF DESCRIPTION OF DRAWINGS

[0012] Embodiments of the utility model will now be described by reference to the accompanying drawings, in which:

[0013] Figure 1 is an exploded perspective view of an embodiment of a PTC heating device, and in which

[0014] Figure 2 and Figure 3 is a diagram illustrating an electric heating device of the utility model.

[0015] LIST OF REFERENCE SIGNS

[0016] 10 PTC heating device

[0017] 12 positioning frame

[0018] 14 receptacle

[0019] 16 PTC element

[0020] 18 main side surface

[0021] 20 conductor

[0022] 20.1 first sheet metal conductor

[0023] 20.2 second sheet metal conductor

[0024] 22 contact lug

[0025] 24.1 first electrically insulating sheet element

[0026] 24.2 second electrically insulating sheet element

[0027] 26 plastic tube

[0028] 28 ceramic plate

[0029] 30 layered structure

[0030] 32.1 first heat dissipating element

[0031] 32 second heat dissipating element

[0032] 34 frame-shaped housing part

[0033] 36 heating chamber

[0034] 40 housing

[0035] 42 frame member

[0036] 44 transverse frame member

[0037] 46 connecting chamber DETAILED DESCRIPTION

[0038] In Figure 1 the drawing, reference 10 identifies a PTC heating device having a positioning frame 12 made of a plastic material, thereby providing three receptacles 14 for PTC elements 16 having opposite main side surfaces 18, the main side surfaces 18 of the cubic PTC elements 16 each having a surface area that is at least four times larger than the surface area of any other surface of the PTC elements 16. Adjacent to those main side surfaces 18 and on both sides of the PTC elements 16, conductors 20 are provided in the form of a first sheet metal conductor 20.1 and a second sheet metal conductor 20.2. The respective sheet metal conductors 20.1, 20.2 each provide a contact lug 22 protruding one end of the positioning frame 12.

[0039] Figure 2A further embodiment of an electric heating device is shown, wherein the first sheet metal conductor 20.1 and the second sheet metal conductor 20.2 are covered by a first and a second insulating sheet element 24.1, 24.2, which are plates made of aluminum oxide.

[0040] Figure 1 and Figure 2 The reference 26 in both figures identifies a plastic tube made of a heat-shrinkable electrically insulating plastic material. The respective plastic tube 26 will be provided with an inner diameter which allows the layers provided by the PTC element 16, the sheet metal conductors 20.1, 20.2 and, if applicable, the first and second electrically insulating sheet elements 24.1, 24.2 (see Figure 2 ) together with the positioning frame 12 to be introduced into the plastic tube 26.

[0041] The plastic tube 26 is then heated, thereby causing the different layers of the PTC heating device 10 to shrink radially and to be biased against each other, to thereby provide a good thermal contact between the PTC element 16 and the sheet metal conductors 20.1, 20.2 on both sides, as well as between the PTC element 16, the respective sheet metal conductors 20.1, 20.2 and the electrically insulating sheet elements 24.1, 24.2.

[0042] Figure 2 The electrically insulating sheet elements 24.1, 24.2 of the embodiment of Figure 2 may also each be formed by a combination of a ceramic plate and a plastic foil or a plastic foil. In addition to the electrically insulating sheet elements 24.1, 24.2 of the embodiment of

[0043] In Figure 3 , the reference 30 identifies a layered structure comprising the PTC heating device 10 and a heat-dissipating element 32, in particular a corrugated heat-dissipating layer, which is at least partially in contact with the outer circumferential surface of the plastic tube 26 of each PTC heating device 10. In Figure 3 , a first heat-dissipating element 32.1 is arranged on one side of one of the PTC heating devices 10 and a second heat-dissipating element 32 is arranged on the other side of one of the PTC heating devices 10.

[0044] The layered structure 30 is received within a frame-shaped housing part 34 which defines a heating chamber 36 and forms part of a housing 40. The layered structure 30 is held within the housing 40 such that each of the layers of the layered structure 30 abuts against an adjacent layer under a pre-tension. To this end, the layered structure 30 can comprise at least one layer which contains spring elements. Alternatively or in addition, opposite frame members 42 of the frame-shaped housing part 34 can have elastic properties such that the layered structure 30 is under a pre-tension.

[0045] As will be apparent from the above, Figure 3 It is apparent that the contact lugs 22 extend beyond the transverse frame members 44 of the frame-shaped housing part 34 and into a connection chamber 46 provided by the housing 40 and containing a control device in the form of a PCB (not shown) which regulates the electrical power supplied to each or a plurality of PTC heating devices 10 which can be combined in a heating circuit.

[0046] According to one aspect of the utility model, a method for manufacturing a PTC heating device 10 is provided, wherein conductors 20 assigned to different electrical polarities are electrically connected to at least one PTC element 16 and are introduced into a tube 24 made of an electrically insulating shrinkable plastic material, in which method the tube 24 is shrunk to provide a tight circumferential sleeve around the at least one PTC element 16 and the conductors 20.

[0047] In the method according to the above aspect, at least one electrically insulating cover 21 is arranged opposite at least one main side surface 18 of the PTC element 16, and wherein the at least one electrically insulating cover 21 is introduced into the tube 24 together with the conductors 20 and the at least one PTC element 16 prior to shrinking.

[0048] In the method according to the above aspect, the conductors 20 are formed as a first sheet metal conductor 20.1 and a second sheet metal conductor 20.2, wherein a first electrically insulating sheet element 22.1 is arranged opposite one main side surface 18 of the PTC element 16 and a second electrically insulating sheet element 22.2 is arranged opposite the opposite main side surface 18 of the PTC element 16, and wherein the first sheet metal conductor 20.1 and the second sheet metal conductor 20.2 and the first electrically insulating sheet element 22.1 and the second electrically insulating sheet element 22.2 are pre-tensioned against the main side surfaces 18 of the PTC element 16 during shrinking.

Claims

1. A PTC heating device (10), comprising: at least one PTC element (16); a conductor (20) assigned to different electrical polarities and electrically connected to the PTC element (16); and an electrical insulator covering the PTC element (16) and the conductor (20). It is characterized in that The electrical insulator is a tube (24) made of a shrinkable plastic material adapted to reduce at least the diameter of the tube (24) via shrinkage, and the tube (24) shrinks around the PTC element (16) and the conductor (20).

2. The PTC heating device (10) according to claim 1, characterized in that At least one electrically insulating cover is arranged opposite to at least one main side surface (18) of the PTC element (16), and the at least one electrically insulating cover is arranged within the shrunk tube (24).

3. The PTC heating device (10) according to claim 1, characterized in that The conductors (20) are sheet metal conductors (20.1, 20.2) and are held in contact with the PTC element (16) by radial pretensioning applied by the shrinking tube (24).

4. The PTC heating device (10) according to claim 1, characterized in that The conductors (20) are sheet metal conductors (20.1, 20.2), a first electrically insulating sheet element (22.1) is arranged opposite one main side surface (18) of the PTC element (16), and a second electrically insulating sheet element (22.2) is arranged opposite the opposite main side surface (18) of the PTC element (16), and the sheet metal conductors (20.1, 20.2) and the first electrically insulating sheet element (22.1) and the second electrically insulating sheet element (22.2) are held in contact with the PTC element (16) by a radial pretension applied by the contracting tube (24).

5. An electric heating device having a housing (40) defining a heating chamber (36), characterized in that: The heating chamber (36) accommodates at least one PTC heating device (10) according to claim 1, wherein the outer circumferential surface of the shrunk tube (24) is exposed in the heating chamber.

6. The electric heating device according to claim 5, characterized in that: A first heat dissipation element (32.1) and a second heat dissipation element (32.2) are arranged in the housing (40), and the first heat dissipation element (32.1) contacts an outer circumferential surface of the tube (24) opposite to one main side surface (18) of the PTC element (16), and the second heat dissipation element (32.2) contacts an outer circumferential surface of the tube (24) opposite to the first heat dissipation element (32.1).

7. The electric heating device according to claim 6, characterized in that: The housing (40) has a frame in which a layered structure (30) comprising at least one PTC heating device (10) and the first heat dissipation element (32.1) and the second heat dissipation element (32.2) is held under pretension such that the first heat dissipation element (32.1) and the second heat dissipation element (32.2) are biased against a main side surface (18) of the PTC element (16).

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