PTC Heating Assembly and Method for Manufacturing the Same

Abstract

A PTC heating assembly includes a heating cell comprising a PTC element and conductor elements electrically abutting the PTC element. The heating cell is accommodated in a heater housing. The heater housing is manufactured with undersize relative to the heating cell so that the heating cell, after insertion into the heater housing, is held under pretension between mutually opposing walls of the heater housing. Accordingly, in the method according to the invention, the heater housing is elastically widened when the heating cell is inserted into the heater housing.

Claims

1. A PTC heating assembly comprising: a heating cell comprising a PTC element and conductor elements electrically abutting the PTC element, wherein the heating cell is accommodated in a heater housing, and wherein the heater housing is manufactured with undersize relative to the heating cell so that the heating cell, after insertion into the heater housing, is held under pretension between mutually opposing walls of the heater housing.

2. The PTC heating assembly according to claim 1, wherein the mutually opposing walls of the heater housing are provided with an electrically insulating coating.

3. The PTC heating assembly according to claim 1, wherein an outside of the heating cell is provided with an electrically insulating layer connected to the PTC element or the associated conductor element.

4. The PTC heating device according to claim 1, wherein the heater housing is formed by a flat tube which is closed on one side, and wherein mutually opposing inner surfaces of the flat tube abut against the heating cell in a heat-conducting manner and are spaced apart from one another by a smaller distance than a thickness of the heating cell.

5. The PTC heating device according to claim 4, wherein the flat tube has an insertion opening which has a larger clear width than the distance between the inner surfaces.

6. The PTC heating device according to claim 4, wherein the heating cell has a frame-shaped casing which joins the PTC element and the strip conductors in a heat-conducting manner as a unit and which is surmounted by contact strips which are electrically conductively connected to the strip conductors for energizing the PTC element with different polarity, and wherein the frame-shaped casing has a wedge-shaped leading frame member which can be inserted first into the insertion opening and which is configured to be adapted for spreading the inner surfaces of the flat tube.

7. The PTC heating device according to claim 6, wherein the frame-shaped casing has a trailing frame member which is inserted as a plug into the flat tube.

8. The PTC heating device according to claim 7, further comprising a sealing collar which seals the flat tube, at least around an outside of the flat tube in the region of the insertion opening.

9. The PTC heating device according to claim 8, wherein the sealing collar is arranged at a height of the trailing frame member.

10. The PTC heating device according to claim 6, wherein the PTC element further comprises insulating layers abutting against the PTC element.

11. A method for producing a PTC heating assembly having a heater housing in which a heating cell is accommodated, the heating cell comprising a PTC element and conductor elements electrically abutting the the PTC element, the method comprising: inserting the heating cell into the heater housing; and elastically expanding the heater housing when the heating cell is inserted into the heater housing so that opposite walls of the heater housing abut the heating cell under pretension after the heating cell has been inserted into the heater housing.

12. The method according to claim 11, wherein the heater housing is formed by a flat tube which is closed on one side, wherein inner surfaces of the flat tube lie opposite one another and abut against the heating cell in a heat-conducting manner and are spaced apart from one another by a smaller distance than a thickness of the heating cell, wherein an insertion opening of the flat tube has a larger clear width than a distance between the inner surfaces of the flat tube, and wherein the heating cell is inserted with clearance into the insertion opening and, with increasing insertion movement, the heating cell elastically presses outwards the inner surfaces of the of the flat tube outwards so that, in the installation position thereof, the heating cell is applied under pretension against the inner surfaces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Further details and advantages of the present invention shall arise from the following description of an embodiment of the invention in combination with the drawing, in which:

[0034] FIG. 1 shows a perspective exploded view of the embodiment of a heating cell;

[0035] FIG. 2 shows a perspective side view of the embodiment of a PTC heating device shown in FIG. 1 prior to being joined with a flat tube;

[0036] FIG. 3 shows the illustration according to FIG. 2 in a longitudinal sectional view;

[0037] FIG. 4 shows the illustration according to FIG. 3 after joining;

[0038] FIG. 5 shows a perspective side of the embodiment of a PTC heating device.

DETAILED DESCRIPTION

[0039] The embodiment according to FIG. 1 shows a housing 2 made of plastic, which is configured as a frame and forms an accommodation space 4 to accommodate PTC elements 6. The two PTC elements 6 are each cuboid in shape and have opposing surfaces 8, which define the main side surfaces of the PTC elements 6 that predominantly emit the heat and which are connected to each other by circumferential end surfaces 10. Opposite the surface 8, conductor tracks in the form of contact plates 12 are shown, each of which has a contact strips 14 formed by punching and bending the sheet material. Corresponding to these contact strips 14, the housing is provided with 2 connecting pieces 16 which accommodate the respective contact strips 14 so that the free end of the contact strips 14 protrudes beyond the housing 2. These free ends of the terminal lugs 14 are used to energize the PTC elements 6 within the housing 2. After the contact strips 14 have been inserted, the connecting pieces 16 are covered with a lid 17, which is attached to the housing by hot caulking of pins that protrude from the housing 2 and each pass through a bore in the lid 17.

[0040] Reference sign 18 shows insulating layers in the form of aluminum oxide plates whose base area is larger than the base area of the contact plates 12 (without the contact strips 14) and which at least partially cover the frame-shaped housing 2 in the assembled state.

[0041] The above-discussed unit is first prefabricated and then inserted into a metal housing 20 made of a sheet metal material, over which a sealing collar 22 made of a soft elastic plastic is drawn at the end in order to insert the heat-generating element identified by reference sign 24 into a receiving pocket of a partition wall, as described in DE 10 2016 224 296 A1, for example.

[0042] The casing 2 has a leading frame member which is identified by reference number 26 and which is tapered towards the front and thus wedge-shaped. In FIG. 1, the tapered end points in the direction of the flat tube 20. Reference sign 28 in FIG. 1 indicates a trailing frame member which is arranged opposite the leading frame member 26 and is merely overhung by the connecting pieces 16. The widened end of the forward frame member 26 merges without a shoulder into a heat-emitting open surface 30. This open surface 30 is formed by the outer surface of the respective aluminum oxide plates 18.

[0043] The wedge shape of the leading frame member 26 allows the heating cell 22 to be centered during insertion into a receiving pocket 31 formed by the flat tube 20. This centering is shown in FIG. 3. Apparently, the central longitudinal axis of the heating cell 22 is aligned with the central longitudinal axis of the flat tube 20. The leading frame member 26 lies with slight clearance within an insertion opening 32 of the flat tube 20, which leads to the receiving pocket 31.

[0044] The flat tube 20 is usually formed by deep-drawing an initially cylindrical semi-finished product, the main side surfaces of which are formed such that the inner surfaces 34 are formed towards each other.

[0045] Starting from the initial position shown in FIG. 3, in which the leading frame member 26 is already in the insertion opening 32, the heating cell 22 is inserted into the flat tube 20. In this context, the leading frame member 26 presses outwards inner surfaces 34 which delimit the receiving pocket 31 and the distance between which is less than the thickness of the heating cell 22 in the sectional view according to FIG. 3. The inner surfaces 34 are elastically pretensioned. In the course of the progressive insertion movement, the inner surfaces 34 are applied against the free surfaces 30. The insertion movement is completed when the leading frame member 26 abuts against a lower closed end of the receiving pocket 31 or a widened collar of the trailing frame member 28 is applied against the insertion opening 32 at the end face. As shown in FIG. 4, accordingly, the inner surfaces 34 fully abut against the free surfaces 30 due to elastic deformation. This ensures good heat extraction from the heat generated by the PTC element 6 to the outer surface of the flat tube 20. Following this joining, the sealing collar 24 is pushed over the flat tube 20. Accordingly, the sealing collar 24 abuts circumferentially against the flat tube 20 at the height of the trailing frame member 28.

[0046] The inner surfaces 34 may be formed to be slightly convex, thus, convex in the direction of the receiving pocket 31, prior to insertion of the heating cell 22.

[0047] FIG. 5 shows a perspective top view onto a heating device housing marked with reference numeral 40 of an electric heating device formed as a water heater. The heater housing 40 has a casing tub element 42 made of plastic material. The heating device housing 40 forms an inlet port 44 and an outlet port 46 which are presently embodied formed integrally on the casing tub element 42. The ports 44, 46 are designed as hose connection ports and form an inlet opening 48 and an outlet opening 50, respectively, to a heating chamber designated with reference numeral 52.

[0048] The heating chamber 52 is separated from a connection chamber 54 and sealed thereagainst by a partition wall 56 made of plastic material. The partition wall 56 forms female plug element holding fixtures 58 for PTC heating elements 22 which are inserted into the female plug element holding fixtures 58, sealed therein by a sealing collar 24 and supported on a base 62 of the casing tub element 42. Reference numeral 64 identifies a control housing, described in further detail in DE 10 2019 205 848.

[0049] Alternatively, the flat tube 20 can also be connected directly to the partition wall 56 by a material bond, for example by gluing or soldering, instead of using a sealing collar. The partition wall 56 can be made of metal. Only a fluid-tight connection between the flat tube 20 and the partition wall 56 is significant. The flat tube 20 can also be integrally formed with the partition wall 56.